Force Sensing Architectures

ABSTRACT

An electronic device with a force sensing device is disclosed. The electronic device comprises a user input surface defining an exterior surface of the electronic device, a first capacitive sensing element, and a second capacitive sensing element capacitively coupled to the first capacitive sensing element. The electronic device also comprises a first spacing layer between the first and second capacitive sensing elements, and a second spacing layer between the first and second capacitive sensing elements. The first and second spacing layers have different compositions. The electronic device also comprises sensing circuitry coupled to the first and second capacitive sensing elements configured to determine an amount of applied force on the user input surface. The first spacing layer is configured to collapse if the applied force is below a force threshold, and the second spacing layer is configured to collapse if the applied force is above the force threshold.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) of U.S.Provisional Patent Application No. 62/297,676, filed Feb. 19, 2016, andentitled “Force Sensing Architectures, U.S. Provisional PatentApplication No. 62/395,888, filed Sep. 16, 2016, and entitled“Force-Sensitive Structure in an Electronic Device,” and U.S.Provisional Patent Application No. 62/382,140, filed Aug. 31, 2016, andentitled “Force Sensing Architectures,” the contents of all of which areincorporated by reference as if fully disclosed herein.

FIELD

The disclosure relates generally to sensing a force exerted against asurface, and more particularly to sensing a force through capacitivechanges.

BACKGROUND

Touch devices generally provide for identification of positions wherethe user touches the device, including movement, gestures, and the like.As one example, touch devices can provide information to a computingsystem regarding user interaction with a graphical user interface (GUI),such as pointing to elements, reorienting or repositioning thoseelements, editing or typing, and other GUI features. As another example,touch devices can provide information to a computing system suitable fora user to interact with an application program, such as relating toinput or manipulation of animation, photographs, pictures, slidepresentations, sound, text, other audiovisual elements, and otherwise.

Generally, however, touch inputs are treated as binary inputs. A touchis either present and sensed, or it is not. A force of a touch input mayprovide another source of input information to a device. For example, adevice may respond differently to a touch with a low application forcethan to a touch with a high application force. Force sensing devices maydetermine an amount or value of an applied force based on an amount ofdeformation of a component that is subjected to the force.

In devices where force inputs are applied to a touchscreen, such as amulti-touch touchscreen that the user touches to select or interact withan object or application displayed on the display, the noise produced bythe display can interfere with the operation of the touchscreen. In somesituations, the display noise can electrically couple to the touchscreenand interfere with the operation of the touchscreen. Such display noisecan also electrically couple to a force sensing device. The magnitude ofthe display noise can be much greater than the magnitude of the forcesignals, making it difficult to discern the force signals from thedisplay noise.

SUMMARY

An electronic device includes a user input surface defining an exteriorsurface of the electronic device, a first capacitive sensor comprising afirst pair of sensing elements having an air gap therebetween andconfigured to determine a first amount of applied force on the userinput surface that results in a collapse of the air gap, and a secondcapacitive sensor below the first capacitive sensor comprising a secondpair of sensing elements having a deformable element therebetween andconfigured to determine a second amount of applied force on the userinput surface that results in a deformation of the deformable element.

The first pair of sensing elements comprises a shared sense element anda first drive element set apart from and capacitively coupled to theshared sense element. The second pair of sensing elements comprises theshared sense element and a second drive element set apart from andcapacitively coupled to the shared sense element. The shared senseelement may be disposed between the first drive element and the seconddrive element. The shared sense element may include an array of sensingregions.

The electronic device may further include a display element coupled tothe first drive element. The electronic device may further include abase structure, wherein the display element is configured to flexrelative to the base structure, the deformable element is coupled to thebase structure, and the air gap is positioned between the deformableelement and the display element. The shared sense element may be coupledto the deformable element.

The electronic device may further include a display layer comprising adisplay element positioned below the user input surface and a backpolarizer positioned below the display element. The electronic devicemay also include a sheet of conductive material formed over a backsurface of the back polarizer to produce a conducting surface on theback surface of the back polarizer, and a conductive border formed alongat least one edge of the sheet of conductive material. The conductiveborder may be positioned outside of a user-viewable region of thedisplay layer. The sheet of conductive material may comprise silvernanowire.

A capacitive force sensor for an electronic device includes a firstdrive layer, a second drive layer positioned relative to the first drivelayer, a shared sense layer between the first and second drive layers, afirst spacing layer between the first drive layer and the shared senselayer, and a second spacing layer between the shared sense layer and thesecond drive layer.

The first spacing layer may comprise an air gap. The capacitive forcesensor may further comprise a pair of opposed surfaces defining the airgap, and an anti-adhesion layer configured to prevent adhesion betweenthe opposed surfaces. The air gap may have a thickness of about 1.0 mmor less. The second spacing layer may comprise a deformable material.The second spacing layer may comprise an array of deformable protrusionsextending from a base layer.

The capacitive force sensor may further include sensing circuitryoperatively coupled to the first drive layer, the second drive layer,and the shared sense layer, and configured to determine a first amountof applied force resulting in a change in thickness of the first spacinglayer and a second amount of applied force resulting in a change inthickness of the second spacing layer.

The first drive layer may include an insulating substrate, a sheet ofconductive material formed over a back surface of the insulatingsubstrate to produce a conducting surface on the back surface of theinsulating substrate, and a conductive border formed along at least oneedge of the sheet of conductive material. The conductive border mayinclude a continuous conductive border that extends along the edges ofthe sheet of conductive material. The conductive border may include oneor more conductive strips formed along a respective edge of the sheet ofconductive material

An electronic device may include a cover defining a user input surfaceof the electronic device, a first sensing element coupled to the coverwithin an interior volume of the electronic device, a frame membercoupled to the cover and extending into the interior volume of theelectronic device, a second sensing element coupled to the frame member,and a third sensing element coupled to a base structure and set apartfrom the sense layer.

The frame member may define an opening, and the third sensing elementmay capacitively couple with the second sensing element through theopening.

The first sensing element may comprise a continuous layer of transparentconductive material covering substantially an entire surface of asubstrate. The second sensing element may comprise a plurality ofsensing regions, and the continuous layer of transparent conductivematerial may overlap multiple sensing regions of the plurality ofsensing regions.

The third sensing element may comprise a plurality of drive regions, andeach drive region may overlap multiple sensing regions of the pluralityof sensing regions. The first sensing element may further comprise aconnection element electrically coupled to the continuous layer oftransparent conductive material, and the electronic device may furthercomprise sensing circuitry configured to provide an electrical signal tothe first sensing element and a connector segment electrically couplingthe sensing circuitry to the connection element.

An electronic device may include an insulating substrate positionedbelow a cover layer, a sheet of conductive material formed over a backsurface of the insulating substrate to produce a conducting surface onthe back surface of the insulating substrate, a conductive border formedalong at least one edge of the sheet of conductive material, and anelectrode layer positioned below the insulating substrate, wherein thesheet of conductive material and the electrode layer together form aforce-sensitive structure that is configured to detect a force input onthe cover layer.

The electronic device may further include drive circuitry coupled to thesheet of conductive material, and sense circuitry coupled to theelectrode layer. The electrode layer may comprise an array ofelectrodes. The conductive border may comprise a continuous conductiveborder that extends along the edges of the sheet of conductive material.The conductive border may comprise one or more conductive strips formedalong a respective edge of the sheet of conductive material.

An electronic device includes a display layer, comprising a displayelement positioned below a cover layer and a back polarizer positionedbelow the display element, a sheet of conductive material formed over aback surface of the back polarizer to produce a conducting surface onthe back surface of the back polarizer, a conductive border formed alongat least one edge of the sheet of conductive material, and a firstelectrode layer positioned below the display layer. The sheet ofconductive material and the first electrode layer together may form aforce-sensitive structure that is configured to detect a force input onthe cover layer.

The electronic device may further comprise a touch-sensitive layerpositioned between the cover layer and the front polarizer. Theelectronic device may further comprise a conductive layer positionedbetween the touch-sensitive layer and the front polarizer. Theconductive border may comprise a continuous conductive border thatextends along the edges of the sheet of conductive material. Theconductive border may comprise one or more conductive strips formedalong a respective edge of the sheet of conductive material.

The force-sensitive structure may comprise a first force-sensitivestructure, the force input may comprise a first amount of force, and theelectronic device may further comprise a second force-sensitivestructure comprising a second electrode layer positioned below andspaced apart from the first electrode layer. The second force-sensitivestructure may be configured to detect a second amount of force on thecover layer, wherein the second amount of force is greater than thefirst amount of force. The conductive border may be positioned outsideof a user-viewable region of the display layer.

The electronic device may further comprise drive circuitry coupled tothe sheet of conductive material and sense circuitry coupled to thefirst electrode layer. The first electrode layer may comprise an arrayof electrodes. The sheet of conductive material may comprise silvernanowire.

A method of forming conductive borders on a surface of a film substratemay include applying a plurality of masks to the surface of the filmsubstrate, each mask defining an area of the surface of the filmsubstrate that will be surrounded by a respective conductive border,forming a conductive material over the surface of the film substrate andthe masks, removing each mask from the surface of the film substrate toproduce the conductive borders, and singulating the conductive bordersto produce individual sections of the film substrate that each includesa respective conductive border. The method may further include forming aprotective layer over the surface of the film prior to singulating theconductive borders.

Forming the conductive material over the surface of the film substrateand the masks may comprise blanket depositing the conductive materialover the surface of the film substrate and the masks. The film substratemay comprise a polarizer film with a sheet of conductive material formedon the surface of the polarizer film. The polarizer film may be attachedto a display element in an electronic device.

An electronic device may comprise a user input surface defining anexterior surface of the electronic device, a first capacitive sensingelement, a second capacitive sensing element capacitively coupled to thefirst capacitive sensing element, a first spacing layer between thefirst and second capacitive sensing elements, a second spacing layerbetween the first and second capacitive sensing elements and having adifferent composition than the first spacing layer, and sensingcircuitry coupled to the first and second capacitive sensing elementsconfigured to determine an amount of applied force on the user inputsurface. The first spacing layer may be configured to collapse if theapplied force is below a force threshold, and the second spacing layermay be configured to collapse if the applied force is above the forcethreshold.

The exterior surface may deflect substantially linearly with respect toforce when the applied force is below the force threshold, and theexterior surface may deflect substantially non-linearly with respect toforce when the applied force is above the force threshold. The sensingcircuitry may determine the amount of applied force using differentforce-deflection correlations based on whether the first spacing layeris fully collapsed.

The first spacing layer may be an air gap, and the second spacing layermay comprise a deformable element. The deformable element may comprisean array of deformable protrusions extending from a base layer. Theelectronic device may further include a sensor configured to detectwhether the first spacing layer is fully collapsed.

A force sensing device for an electronic device includes a stackcomprising a first capacitive sensing element, a structure below thestack and comprising a second capacitive sensing element capacitivelycoupled to the first capacitive sensing element, an air gap between thestack and the structure, and a contact sensor. The stack may beconfigured to move relative to the structure in response to a forceapplied to a user input surface of the electronic device, therebycausing a change in thickness of the air gap, the first and secondcapacitive sensing elements may be configured to provide a measure ofcapacitance corresponding to the change in thickness of the air gap, andthe contact sensor may be configured to detect contact between the stackand the structure resulting from the air gap being fully collapsed. Theforce sensing device may further include a deformable element betweenthe first and second capacitive sensing elements.

The contact sensor may comprise sensing regions and conductive elementsconfigured to contact the sensing regions when the stack contacts thestructure through the air gap. The force sensing device may furthercomprise a deformable element on a first side of the air gap, whereinthe conductive elements are disposed on the deformable element, and thesensing regions are disposed on a second side of the air gap oppositethe first side. The deformable element may comprise protrusionsextending from a base layer, and the conductive elements may be coupledto the protrusions.

The contact sensor may comprise capacitive sensing regions on a firstside of the air gap and dielectric elements on a second side of the airgap opposite the first side and capacitively coupled with the capacitivesensing regions. The capacitive sensing regions may be integrated withthe first capacitive sensing element, and the dielectric elements arecoupled to the deformable element.

A sensor component for an electronic device may include a base, aplurality of protrusions comprising deformable material extending fromthe base, and a plurality of sense elements disposed at free ends of theprotrusions. The sense elements may be at least partially embedded inthe protrusions. The sense elements may be coated on the protrusions.The sense elements may comprise a conductive material. The senseelements may comprise a dielectric material. The base and the pluralityof protrusions may be a unitary component. The sensor component mayfurther comprise at least one additional protrusion that does notinclude any sense elements.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will be readily understood by the following detaileddescription in conjunction with the accompanying drawings, wherein likereference numerals designate like structural elements, and in which:

FIG. 1 shows an example computing device incorporating a force sensingdevice.

FIG. 2 shows another example computing device incorporating a forcesensing device.

FIGS. 3A-3E show partial cross-sectional views of the device of FIG. 1viewed along line A-A in FIG. 1.

FIG. 4 shows a force versus deflection curve of the device of FIG. 1.

FIG. 5 shows a cross-sectional view of an example force sensing deviceviewed along line A-A in FIG. 1.

FIG. 6 shows a force versus deflection curve of the force sensing deviceof FIG. 5.

FIG. 7 shows an exploded view of the sensing elements of the forcesensing device of FIG. 5.

FIG. 8 shows a partial cross-sectional view of the sensing elements ofFIG. 7 viewed along line C-C in FIG. 7.

FIG. 9 shows a sensing element of the force sensing device of FIG. 5.

FIGS. 10A-10B show embodiments of another sensing element of the forcesensing device of FIG. 5.

FIG. 11 shows yet another sensing element of the force sensing device ofFIG. 5.

FIG. 12 shows a cross-sectional view of another example force sensingdevice viewed along line A-A in FIG. 1.

FIG. 13 shows a force versus deflection curve of the force sensingdevice of FIG. 12.

FIG. 14 shows a cross-sectional view of yet another example forcesensing device viewed along line A-A in FIG. 1.

FIG. 15 shows a force versus deflection curve of the force sensingdevice of FIG. 14.

FIG. 16 shows a cross-sectional view of yet another example forcesensing device viewed along line A-A in FIG. 1.

FIG. 17 shows a force versus deflection curve of the force sensingdevice of FIG. 16.

FIGS. 18A-18B show expanded cross-sectional views of the force sensingdevice of FIG. 17.

FIG. 19 shows a perspective view of a deformable element.

FIG. 20 shows a perspective view of a sensing element.

FIGS. 21A-21B show cross-sectional views of an example contact sensor.

FIGS. 22A-22B show cross-sectional views of another example contactsensor.

FIGS. 23A-23B show partial cross-sectional views of the device of FIG. 1viewed along line A-A in FIG. 1, showing an embodiment with a forcesensing system integrated therein.

FIG. 24 shows a force versus deflection curve of the force sensingsystem of FIGS. 23A-23B.

FIG. 25 shows a sensor of the force sensing system of FIGS. 23A-23B.

FIG. 26 shows a cross-sectional view of an example embodiment of theelectronic device of FIG. 1 viewed along line B-B in FIG. 1.

FIG. 27 depicts a first example arrangement of the conductive border onthe polarizer shown in FIG. 26.

FIG. 28 depicts a second example arrangement of the conductive border onthe polarizer shown in FIG. 26.

FIG. 29 depicts a third example arrangement of the conductive border onthe polarizer shown in FIG. 26.

FIG. 30 shows example components of an electronic device.

FIG. 31 shows an example process for determining an amount of forceapplied to a user input surface.

FIG. 32 shows an example process for manufacturing the conductive borderon a surface of a polarizer.

FIGS. 33A-33B depict the application of masks to a surface of a film.

FIGS. 34A-34B show the formation of the conductive material over thefilm and the masks.

FIGS. 35A-35B show the removal of the masks from the film.

FIGS. 36A-36B show the formation of the protective layer over the filmand the conductive material.

FIGS. 37A-37B show the production of each individual section of filmthat is surrounded by a conductive border.

FIG. 38 shows a first example technique for determining the geometry ofthe conductive border.

FIG. 39 shows a first example technique for determining the geometry ofthe conductive border.

FIG. 40 shows a first example technique for determining the geometry ofthe conductive border.

The use of cross-hatching or shading in the accompanying figures isgenerally provided to clarify the boundaries between adjacent elementsand also to facilitate legibility of the figures. Accordingly, neitherthe presence nor the absence of cross-hatching or shading conveys orindicates any preference or requirement for particular materials,material properties, element proportions, element dimensions,commonalties of similarly illustrated elements, or any othercharacteristic, attribute, or property for any element illustrated inthe accompanying figures.

DETAILED DESCRIPTION

Reference will now be made in detail to representative embodimentsillustrated in the accompanying drawings. It should be understood thatthe following descriptions are not intended to limit the embodiments toone preferred embodiment. To the contrary, it is intended to coveralternatives, modifications, and equivalents as can be included withinthe spirit and scope of the described embodiments as defined by theappended claims.

The present disclosure is related to force sensing devices that may beincorporated into a variety of electronic or computing devices, such as,but not limited to, computers, smart phones, tablet computers, trackpads, wearable devices, small form factor devices, and so on. The forcesensing devices may be used to detect one or more user force inputs onan input surface, and then a processor (or processing unit) maycorrelate the sensed inputs into a force measurement and provide thoseinputs to the computing device. In some embodiments, the force sensingdevices may be used to determine force inputs to a track pad, atouchscreen display, or another input surface.

Devices may be configured to respond to or use force inputs in variousways. For example, a device may be configured to display affordanceswith which a user can interact by touching the surface of a touchscreen.Affordances may include application icons, virtual buttons, selectableregions, text input regions, virtual keys, or the like. The touchscreenmay be able to detect the occurrence and the location of a touch event.By incorporating force sensors such as those disclosed herein, thedevice may be able to not only detect the occurrence and location of atouch, but also an amount of force with which the input is applied. Thedevice can then take different actions based on the amount of appliedforce. For example, if a user touches an application icon with a forceinput below a threshold, the device may open the application. If theuser touches the application icon with a force above the threshold, thedevice may open a pop-up menu containing additional affordances relatedto the application. As another example, force sensors may be used todetermine a weight associated with an applied force, such that a devicecan act as a scale. Other applications for force inputs are alsocontemplated.

The force sensing device may include an input surface, one or moresensing layers (such as capacitive sensing elements, drive layers, senselayers, and the like), one or more spacing layers (e.g., air gaps,deformable elements), and a substrate or support layer. The inputsurface provides an engagement surface for a user, such as the externalsurface of a track pad or the cover glass of a display. The forcesensing device may be incorporated with other components of anelectronic device, such as a touchscreen, a display, or the like. Insuch cases, the components of the force sensing device, such as the oneor more sensing layers, may be interspersed with other layers, such as acover glass, filters, touch sensing layers, backlighting components, adisplay element (e.g., a liquid crystal display assembly), or the like.

A user input applied to an input surface of the force sensing device maycause one or more layers of the force sensing device to deflect in adirection of the applied force such that a spacing layer (e.g., an airgap) is collapsed. This deflection changes the distance betweencomponents of the force sensing device, such as between twocomplementary sensing layers, which can be detected by the force sensingdevice and correlated to a particular applied force. When the spacinglayer has been fully collapsed (e.g., the components defining oppositesides of the gap have come into contact with each other), additionalforce applied to the input surface will not result in a significantadditional change in distance between the layers of the force sensingdevice. That is, the force sensing device has reached the maximum valueof force that it can detect.

Force sensing devices described herein include a first spacing layer,such as an air gap, and a second spacing layer, such as a deformableelement, that produce a progressive deformation response to an appliedforce. For example, an air gap and a deformable element may be disposedbetween the first and second sensing layers such that an applied forcefirst causes the air gap to collapse, and, once the air gap has fullycollapsed, causes the deformable element to compress or otherwisedeform. As the applied force increases and the deformable elementbecomes more compressed, the deformable element imparts a progressivelyhigher reaction force against the applied force. Thus, a force sensingdevice with a deformable element and an air gap may be able to sense alarger force for a given deflection than would be possible in a similarforce sensing device without the deformable element.

Force sensing devices described herein may also include contact sensorsthat indicate when adjacent layers defining an air gap come into contactwith each other (e.g., when the air gap has been fully collapsed). Suchcontact sensors may be used to indicate to a processor or sensingcircuitry whether the force sensing device is operating in an air-gapforce regime or a deformable-element force regime, which may improve thequality and/or accuracy of the force sensing device.

Air gaps, deformable elements, and contact sensors may be used invarious different force sensing architectures having various numbers andarrangements of spacing layers, sensing layers, contact sensors, and thelike. Examples of such architectures are described herein.

FIGS. 1-2 show example electronic devices that may incorporate the forcesensing devices described herein. For example, FIG. 1 shows anelectronic device 100 (e.g., a mobile computing device) that mayincorporate the force sensing devices described herein. The electronicdevice 100 may include a housing 104 and a display 102. The display 102can provide a visual output to a user in a user-viewable region 108. Thedisplay 102 can be implemented with any suitable technology, including,but not limited to, a multi-touch sensing touchscreen that uses a liquidcrystal display (LCD) element, a light emitting diode (LED) element, anorganic light-emitting display (OLED) element, an organicelectroluminescence (OEL) element, and the like. In some embodiments,the display 102 can function as an input device that allows the user tointeract with the mobile computing device 100. For example, the displaycan be a multi-touch touchscreen LED display.

The device 100 may also include an I/O device 106. The I/O device 106can take the form of a home button, which may be a mechanical button, asoft button (e.g., a button that does not physically move but stillaccepts inputs), an icon or image on a display, and so on. Further, insome embodiments, the I/O device 106 can be integrated as part of acover 110 and/or the housing 104 of the electronic device. The device100 may also include other types of I/O devices, such as a microphone, aspeaker, a camera, a biometric sensor, and one or more ports, such as anetwork communication port and/or a power cord port.

The cover 110 may be positioned over the front surface (or a portion ofthe front surface) of the device 100. At least a portion of the cover110 can function as an input surface that receives touch and/or forceinputs. The cover 110 can be formed with any suitable material, such asglass, plastic, sapphire, or combinations thereof. In one embodiment,the cover 110 covers the display 102 and the I/O device 106. Touch andforce inputs can be received by the portion of the cover 110 that coversthe display 102 and by the portion of the cover 110 that covers the I/Odevice 106.

In another embodiment, the cover 110 covers the display 102 but not theI/O device 106. Touch and force inputs can be received by the portion ofthe cover 110 that covers the display 102. In some embodiments, the I/Odevice 106 may be disposed in an opening or aperture formed in the cover110. The aperture may extend through the housing 104 one or morecomponents of the I/O device 106 can be positioned in the housing 104.

A force sensing device may be configured to detect force inputs on thedisplay 102. A force sensing device may also be configured to detectforce inputs on a portion of the housing 104, such as a back or side ofthe housing 104, or a bezel portion surrounding the display 102. Inaddition to the force sensing device, the display 102 may also includeone or more touch sensors, such as a multi-touch capacitive grid, or thelike. In these embodiments, the display 102 may detect both force inputsas well as position or touch inputs. The device 100 in FIG. 1 isembodied as a tablet computer (e.g., a mobile computing device), butthis is merely one example device that may include the force sensingdevices described herein. Examples of other devices that may include theforce sensing devices described herein include other mobile computingdevices, wearable electronic devices (e.g., watches), mobile phones,laptop or desktop computers, computer peripherals (e.g., trackpads thatprovide input to computers), or the like.

FIG. 2 shows a laptop computer 200 that includes a trackpad 206 (orother input surface), a display 202, and an enclosure 204. The enclosure204 may extend around a portion of the trackpad 206 and/or the display202. Force sensing devices may be configured to detect force inputs onthe trackpad 206, the display 202, or both.

In another example (not shown), a force sensing device may beincorporated into a trackpad that is connectible to a computer, buthoused in a separate enclosure or housing. For example, a standalonetrackpad that includes a force sensing device may be configured to beconnected to a computer as a peripheral input device, similar to a mouseor trackball.

FIG. 3A is a cross-sectional view of the device 100 viewed along lineA-A in FIG. 1, showing an assembly 300 that may provide display, touchsensing, and force sensing functionality to the device 100, or may beintegrated with other components to provide such functionality. Forexample, FIGS. 5, 12, 14, 16, 23A, and 26 illustrate examples of forcesensing structures and/or devices that may be integrated with theassembly 300 or an assembly similar to the assembly 300.

The device 100 includes a cover 303 coupled to the housing 104 anddefining an external surface of the device 100. The cover 303 may be asingle layer or it may include multiple layers, and may be formed fromor include any appropriate material(s), such as glass, treated glass,plastic, diamond, sapphire, ceramic, oleophobic coatings, hydrophobiccoatings, or the like. The device 100 may also include other internalcomponents, including circuit boards, cameras, sensors, antennas,processors, haptic elements, speakers, or the like, which are omittedfrom FIG. 3A for clarity.

The cover 303 may be coupled to the housing 104 via an interfacingmember 305. FIG. 3B is an expanded view of the area 317 shown in FIG.3A, showing the joint between the cover 303 and the housing 104 ingreater detail.

The interfacing member 305 may be or may include an adhesive that fixesthe cover 303 to a ledge 307 or other feature of the housing 104. Forexample, the interfacing member 305 may be a pressure sensitive adhesive(PSA), heat sensitive adhesive (HSA), epoxy, or other bonding agent. Theinterfacing member 305 may be compliant or rigid. Where the interfacingmember 305 is compliant, it may help protect the cover 303 (which mayinclude glass or other breakable materials) from damage due to shocksand impacts. Moreover, as discussed herein with reference to FIGS.23A-25, the interfacing member 305 may include or cooperate with sensingelements that, along with appropriate processing circuitry, can detect adegree of deformation of the interfacing member 305. The detected degreeof deformation of the interfacing member 305 can then be used todetermine information such as an amount of force applied to the cover303.

With reference to FIG. 3A, the assembly 300 includes an upper stack 304,which may include one or more layers or components of a display,including a liquid crystal matrix, light emitting diodes (LEDs), lightguides, filters (e.g., polarizing filters), diffusers, electrodes,shielding layers (e.g., layers of indium tin oxide), or the like. Theupper stack 304 may be coupled to the cover 303, such as with PSA, HSA,or the like. The upper stack 304 may also include sensing elements fordetecting the presence and/or location of a touch input on the cover303, including, for example, capacitive sensing elements, resistivesensing elements, and the like.

The assembly 300 also includes a lower stack 308, which may be separatedfrom the upper stack 304 over at least a portion of the lower stack 308by an air gap 306. The air gap 306 that separates the upper and lowerstacks 304, 308 may be approximately 25 microns to approximately 100microns thick, though other dimensions are also possible. The air gap306 may help prevent deformation of components in the lower stack 308 inresponse to an applied force on the cover 303 which may causeundesirable optical artifacts on the display 102. For example, the lowerstack 308 may include light sources, light guides, diffusers, or otheroptical components that, if rigidly coupled to the upper stack 304, maydeflect when a force is applied to the cover 303. By separating theseelements from the upper stack 304 by the air gap 306, undesirabledeformations may be reduced.

The lower stack 308 may include a frame member 309 that supports othercomponents of the lower stack 308 and couples the lower stack 308 to theupper stack 304. For example, the frame member 309 may supportcomponents of the lower stack 308 (including light sources, lightguides, diffusers, sensing elements, or the like) in a spaced apartconfiguration relative to the upper stack 304 and/or the cover 303.

The frame member 309 may be coupled to the upper stack 304 and/or thecover 303 and may extend into an interior volume of an electronicdevice. The frame member 309 may be coupled to the upper stack 304and/or the cover 303 by a joining member 311, which may be or include anadhesive or other bonding agent. The frame member 309 may be formed fromor include any appropriate material, such as metal, plastic, or thelike. As described herein, the assembly 300 may include sensing elementsfor sensing an applied force on the cover 303. Such sensing elements mayrely on the ability to electromagnetically interact with other sensingelements in order to determine the applied force. For example, acapacitive sense layer may need to capacitively couple to a capacitivedrive layer in order to detect a change in distance between the senseand drive layers. Accordingly, the frame member 309 may define anopening in a central portion of the frame member 309. The opening mayreduce or eliminate interference, shielding, or other negative effectsof a solid layer between the sensing elements. As shown, a stiffeningmember 312 formed from dielectric material (or any other material thatdoes not shield or otherwise interfere with the sense and drive layers)is disposed in the opening. In some embodiments, the stiffening member312 may be omitted from the frame member 309, and the opening may remainunfilled.

In cases where the frame member 309 defines an opening to facilitate orimprove electrical, capacitive, and/or electromagnetic interactionbetween sensing elements, the opening may be substantially coincidentwith a display and/or touch-sensitive region of the display 102.Accordingly, sensing elements may be able to provide force (or other)sensing functionality to substantially the entire display and/ortouch-sensitive region of the display 102.

The lower stack 308 may include one or more layers or components of adisplay. For example, the lower stack 308 may include a light source 313comprising one or more LEDs, fluorescent lights, or the like. The lightsource 313 may emit light into an optical stack 315 that includes one ormore optical components including but not limited to reflectors,diffusers, polarizers, light guides (e.g., light guide films), andlenses (e.g., Fresnel lenses). The lighting configuration shown in FIGS.3A-3B is merely exemplary, and the lower stack 308 may include lightingconfigurations other than that shown in FIGS. 3A-3B.

The upper and lower stacks 304, 308 are described above as includingdisplay elements. In applications where the assembly 300 does notprovide display functionality, such as where the assembly 300 is part ofor coupled to the trackpad 206, the upper and lower stacks 304, 308 mayinclude different components and/or layers as those described above, ormay be omitted or replaced with other components.

Below the lower stack 308 are a first spacing layer, such as an air gap310, and a second spacing layer, such as a deformable element 314. Theair gap 310 may be approximately 0.5 to approximately 1.0 mm thick,though other dimensions are also possible.

The first and second spacing layers are configured to change thicknessin response to an applied force. For example, a thickness of the air gap310 (e.g., the distance between the opposed surfaces that define the airgap) may be decreased as a force is applied to the cover 303. Similarly,a thickness of the deformable element 314 may be decreased as a force isapplied to the cover 303.

The deformable element 314 may include any appropriate material, such assilicone, polyurethane foam, rubber, gels, or the like. Moreover, thedeformable element 314 may have any appropriate structure, such asmultiple compliant or deformable protrusions (as shown), which may beformed as columns, beams, pyramids, channels with sidewalls, cones,wave-shaped protrusions, bumps, or the like. The deformable element 314may also or instead comprise open or closed cells, such as a sponge or afoam. The deformable element 314 may also have a substantiallyhomogenous, nonporous composition. As yet another example, thedeformable element 314 may include multiple discrete pieces ofdeformable material, such as dots, pads, or the like.

The foregoing materials and configurations for the first and secondspacing layers are merely examples, however, and the first and secondspacing layers may be formed from any appropriate materials orcombinations thereof. For example, the air gap 310 may be replaced witha first foam material, and the deformable element 314 may include asecond foam material having a different density, thickness, composition,or spring constant, than the first. As another example, the first andsecond spacing layers may be substantially identical, and may include orbe formed from the same materials.

The deformable element 314 may be coupled to or adjacent a basestructure or layer 316. The base structure 316 may be a substrate orsupport layer dedicated to the assembly 300, or it may be anothercomponent of an electronic device, such as a battery, a portion of ahousing or enclosure, a circuit board, or any other component.

FIGS. 3C-3E illustrate a progression of the physical response of theassembly 300 to an input force 302 on the upper stack 304. As notedabove, the input force 302 may correspond to a user contacting a userinput surface of an electronic device, such as the cover 303, with afinger, stylus, or other object. The input force 302 may be transferredthrough the cover 303 to the surface of the upper stack 304.

FIG. 3C illustrates the portion of the assembly 300 represented by area301 in FIG. 3A prior to the input force 302 being applied to the upperstack 304. FIG. 3D illustrates the assembly 300 after the force inputhas caused the upper stack 304 to deflect or flex sufficiently to fullycollapse the air gap 306. In particular, the upper stack 304 has beenflexed towards the lower stack 308 such that the upper stack 304 is incontact with the lower stack 308 in at least one location. The stiffnessof the upper stack 304 and the size of the air gap 306 may determine theamount of force that causes the upper stack 304 to come into contactwith the lower stack 308. In some cases, even a slight touch from theuser will be sufficient (e.g., a touch that a user would not consider tobe “pressing” on the cover).

FIG. 3E illustrates the assembly 300 after the force input has causedthe lower stack 308 to deflect sufficiently to fully collapse the airgap 310, thus bringing the lower stack 308 into contact with and atleast partially deforming the deformable element 314.

As used herein, the term “collapse” may refer to a partial collapse of alayer (e.g., corresponding to any reduction in thickness of a materialor an air gap at any location), or a full collapse of a layer (e.g.,corresponding to opposing surfaces that define an air gap coming intocontact with one another at any point, or reaching a maximum deformationof a deformable material).

FIG. 4 is an example force versus deflection curve illustrating how auser input surface of the assembly 300 (e.g., the cover 303) deflects inresponse to the force input in FIGS. 3C-3E. In particular, as the forceincreases from zero to a force threshold (e.g., corresponding to point402), the deflection increases along a first profile 406. In some cases,the first profile 406 corresponds to the deflection of the assembly 300until all of the air gaps in the assembly 300 (e.g., the air gap 306 andthe air gap 310) have been fully collapsed. As the force increasesbeyond the force threshold (e.g., point 402) and the deformable element314 compresses, the deflection increases along a second profile 408extending from point 402 to point 404. Accordingly, the force thresholdcorresponds to the amount of force at the transition from collapse ofthe air gaps only to deformation of the deformable element.

The first profile 406 may be substantially linear, such that anincremental increase in force produces substantially the sameincremental increase in deformation of the cover 303 at any point in thefirst profile 406. In contrast, the second profile 408 may benon-linear, and may plateau as the force increases. For example, anincremental increase in force at the beginning of the second profile 408may result in a greater amount of deformation of the cover 303 than thesame incremental increase in force at the end of the second profile 408.However, these profiles are merely exemplary, and the force sensingdevices described herein may exhibit any other force versus deflectioncurves or profiles.

The systems and methods described herein, including the force sensingdevices 500, 700, 900, and 1100 described below, facilitate thedetection of whether a force sensing device is operating according tothe first profile 406, such that only air gaps are being collapsed, orthe second profile 408, such that a deformable element is beingdeformed. By detecting the different profiles, accurate forcemeasurements may be provided.

While FIGS. 3A-4 relate to the assembly 300 of the device 100, thecomponents, structures, and principles of operation of the assembly 300may apply to other devices as well, such as the display 202 or thetrackpad 206 of the device 200 (or any other appropriate device). Incases where a display is not present, such as the trackpad 206, somecomponents of the assembly 300 may be omitted, replaced, or rearranged.For example, the upper and lower stacks 304, 308 may include componentsother than display elements, or they may be omitted or replaced withspacers or other components.

FIG. 5 is a partial cross-sectional view of an example force sensingdevice 500 that may be incorporated in an electronic device (e.g., thedevices 100, 200), depicting an area similar to the area 301 in FIG. 3A.The cover 303 and the housing 104 are omitted for clarity.

The force sensing device 500 includes an upper stack 504, similar to theupper stack 304, which may include one or more layers or components of adisplay, including a liquid crystal matrix, light emitting diodes(LEDs), light guides, filters (e.g., polarizing filters), diffusers,electrodes, or the like. The upper stack 504 may be configured to flexor be capable of flexing in response to an applied force on the forcesensing device 500.

A first sensing element 505 is coupled to the upper stack 504 (forexample, to a cover 303 or to a component that is coupled to the cover303, such as a filter) and is within an interior volume of an electronicdevice. The first sensing element 505 may be a capacitive sensingelement that is configured to capacitively couple with anothercapacitive sensing element. For example, the first sensing element 505may be a drive layer that is capacitively coupled to a sense layer(e.g., the second sensing element 512, below) that facilitates detectionof a distance between the sense and drive layers using mutualcapacitance. As another example, the first sensing element 505 may be asense layer instead of a drive layer. As yet another example, the firstsensing element 505 may be configured to capacitively couple to a groundlayer to facilitate detection of a distance between itself and theground layer using self-capacitance. As yet another example, the firstsensing element 505 may be a ground layer that capacitively couples to aseparate sense layer.

In the presently described examples, the sensing elements are describedas elements for capacitive sensing. However, other types of sensors (andsensor components) may be used instead of or in addition to capacitivesensors. Indeed, other types of sensors or sensing technologies that candetect changes in distance, or absolute distance, between components orotherwise detect force may be used. For example, inductive sensors,optical sensors, sonic or ultrasonic sensors, or magnetic sensors may beused. Moreover, the components of the sensors may be integrated in theforce sensors as shown herein (e.g., with sensing elements set apartfrom one another by one or more layers including air gaps, deformablelayers, other components, or the like), or they may be integrated in anyother manner suitable for that type of sensor (e.g., an optical sensormay include one or more light emitters in place of a sensing layer).

The first sensing element 505 may be coupled to the upper stack 504 inany appropriate way, such as with a pressure sensitive adhesive (PSA),heat sensitive adhesive (HSA), or the like. The first sensing element505 may also be patterned on the upper stack 504, such as with physicalvapor deposition, electron beam evaporation, sputter deposition, or anyother appropriate technique. The first sensing element 505 may be formedfrom or include any appropriate material, such as indium tin oxide(ITO), disposed on a substrate.

A lower stack 508 may be disposed below the first sensing element 505and separated from the first sensing element 505 by an air gap 506. Likethe air gap 306, the air gap 506 may be any appropriate thickness, suchas from about 25 microns to about 100 microns.

The lower stack 508 may include any appropriate components or layers,such as those described above with respect to the lower stack 308 (e.g.,LEDs, an optical stack, backlights, reflectors, or light guides), andmay be coupled to the upper stack 504 and/or the housing 104 asdescribed with respect to the lower stack 308 of FIG. 3A (e.g., via theframe member 309). In embodiments where the force sensing device 500does not include a display or does not provide display functionality,lower stack 508 (as well as the upper stack 504) may include differentcomponents or be omitted.

The lower stack 508 may be coupled to and/or supported by a framemember, which may be similar to the frame member 309 in FIG. 3A. Theframe member may include a stiffening member 509, similar to thestiffening member 312 in FIG. 3A. The stiffening member 509 may beformed from or include a dielectric material to facilitate or improveelectrical, capacitive, and/or electromagnetic interaction betweensensing elements (e.g., between the first sensing element 505 and thesecond sensing element 512).

The frame member, and in particular the stiffening member 509, maysupport the lower stack 508 in a spaced apart configuration relative tothe upper stack, a base structure 516, a deformable element 514, orother components of the electronic device. FIG. 5 shows the secondsensing element 512 coupled to a deformable element 514. However, insome cases, the second sensing element 512 may be coupled to the lowerstack 508. In such cases, the second sensing element 512 may be coupledto the frame member, such as to the stiffening member 509 or a componentof the lower stack 508.

An air gap 510 separates the lower stack 508 from a second sensingelement 512. The air gap 510 may be any appropriate thickness, such asfrom about 0.5 mm to 1.0 mm.

The second sensing element 512 may be a sense layer for a capacitivesensor, and may be capacitively coupled to the first sensing element505. The second sensing element 512 may include an array of discretecapacitive sensing regions that facilitate detection of a location(and/or a magnitude) of a force input on the upper stack 504. The secondsensing element 512 may be formed from or include any appropriatematerial, such as ITO traces disposed on a substrate. The second sensingelement 512 may be coupled to the deformable element 514, the stiffeningmember 509 (or other component of the frame member or lower stack 508),or any other component or structure in the interior volume of theelectronic device such that the second sensing element 512 is betweenthe first sensing element 505 and a third sensing element 515 (discussedbelow).

An optional anti-adhesion layer 511 may be disposed on a surfacedefining a side of the air gap 510 in order to prevent the oppositesides of the air gap from sticking together, either temporarily orpermanently, when they contact each other. Thus, when an applied forceis removed from a user input surface, the components of the forcesensing device 500 can return to or near their original orientations.The anti-adhesion layer 511 may be formed from or include anyappropriate material, and may have any appropriate shape or structure.For example, the anti-adhesion layer 511 may comprise posts,protrusions, channels, or other structures that permit airflowtherethrough to reduce or prevent the formation of sealed areas betweenthe surfaces of the air gap 510 when the air gap 510 is fully collapsed.Without the anti-adhesion layer 511, such sealed areas may result innegative pressure zones that could act similar to “suction cups” thatprevent the separation of the sides of the air gap 510. Theanti-adhesion layer 511 may prevent adhesion caused by other mechanismsor forces as well, such as van der Waals forces, electrostatic forces,or the like.

The force sensing device 500 includes a deformable element 514 betweenthe second sensing element 512 and a third sensing element 515. Similarto the deformable element 314, the deformable element 514 may includeany appropriate material (such as silicone, polyurethane foam, rubber,gels, or the like) and may have any suitable structure, such as multiplecompliant columns (as shown), beams, pyramids, cones, wave-shapedprotrusions, open or closed cells, or the like. The deformable element514 may deflect non-linearly with respect to an applied force, asdescribed above.

The deformable element 514 is shown in FIG. 5 below the air gap 510 andbetween the second sensing element 512 and the third sensing element515. However, the relative positions of the air gap 510 and thedeformable element 514 may be swapped. For example, the deformableelement 514 may be coupled to the lower stack 508.

The third sensing element 515, disposed between the deformable element514 and a base structure 516, may be a drive layer for a capacitivesensor, and may be capacitively coupled to the second sensing element512. For example, the second sensing element 512 may be a sense layer,and the third sensing element 515 may be a drive layer, thus forming acapacitive sensor spanning the deformable element 514.

The base structure 516 may be a frame, bracket, or support structure ofthe force sensing device. In some cases, the base structure 516 is acomponent of an electronic device that is beneath a user input surface,such as a circuit board, a battery, an interior wall of a housing orenclosure, or the like. The base structure 516 may be stiffer orotherwise more resistant to deflection in response to an applied forcethan the components above it. Thus, once the air gap 510 has been fullycollapsed, additional force may primarily deform the deformable element514 rather than deflecting the base structure 516.

The first, second, and third sensing elements 505, 512, and 515 may formtwo capacitive sensors. For example, as described above, the first andthird sensing elements 505, 515 may each act as a distinct drive layer,and the second sensing element 512 may be a sense layer thatcapacitively couples to (and senses changes in distance to) both thefirst and third sensing elements 505, 515.

Where the second sensing element 512 is a shared sense layer, it mayinclude a first set of sensors for detecting the distance to the firstsensing element 505 and a second set of sensors for detecting thedistance to the third sensing element 515. The second sensing element512 may also or instead use the same sensors to detect the distance toboth the first and third sensing elements 505, 515. In the latter cases,the first and third sensing elements 505, 515 may be driven withdifferent electrical signals, thus allowing the second sensing element512 (and/or sensing circuitry coupled to the second sensing element 512)to differentiate between capacitance changes that are caused by changesin a size of the air gap 510 and capacitance changes that are caused bychanges in a size of the deformable element 514. In another embodiment(not shown), the second sensing element 512 may be replaced with twodiscrete sensing elements, each acting as a sense layer for a differentone of the first and third sensing elements 505, 515.

FIG. 6 is an example force versus deflection curve illustrating how theforce sensing device 500 in FIG. 5 deflects in response to a force inputapplied (directly or indirectly) to the upper stack 504. The forceresponse is similar to that shown in FIG. 4, with a first profile frompoint 401 to point 402 (corresponding to collapse of the air gaps 506and 510) and a second profile from point 402 to point 404 (correspondingto deformation of the deformable element 514).

As noted above, the force sensing device 500 has two capacitivesensors—a first capacitive sensor 518 formed by the first and secondsensing elements 505, 512, and a second capacitive sensor 519 formed bythe second and third sensing elements 512, 515. The first capacitivesensor 518 spans the air gaps 506 and 510, and the second capacitivesensor 519 spans the deformable element 514. Thus, the first capacitivesensor 518 is positioned within the force sensing device 500 to detectdeformation of the upper stack 504 along the line 602 in FIG. 6, and thesecond capacitive sensor 519 is positioned within the force sensingdevice 500 to detect deformation of the upper stack 504 along the line604 in FIG. 6. By detecting the deformation of the air gaps with onesensor and the deformation of the deformable element with a differentsensor, sensing circuitry can process the signals according to differentforce-deflection correlations. For example, deflections from the firstcapacitive sensor 518 may be correlated to an amount of applied forceaccording to the substantially linear profile between point 401 andpoint 402, and the deflections from the second capacitive sensor 519 maybe correlated to an amount of applied force according to the non-linearprofile between point 402 and point 404. Of course, the linear andnon-linear profiles shown in FIG. 6 are merely examples, and thedeformation of a force sensing device may follow or exhibit differentprofiles.

Sensing circuitry may apply force-deflection correlations in anyappropriate manner. For example, force-deflection correlations may beimplemented in mathematical functions that output a particular forcevalue for a particular determined amount of deflection (which may inturn have been determined based on a measured or detected capacitancevalue, or any other electrical measurement or value). As anotherexample, force-deflection correlations may be implemented using lookuptables, where particular deflection values are correlated withparticular force values. Other techniques are also possible, and theseexamples do not limit the mathematical or programmatic techniques thatmay be used to produce force values from measured or detected electricalproperties (e.g., capacitance, resistance, current, signals, etc.).

FIG. 7 is an exploded view of the sensing elements 505, 512, and 515 ofthe force sensing device 500 of FIG. 5, illustrating exampleconfigurations of the sensing elements in an implementation of the forcesensing device 500 that uses capacitive sensing to detect changes indistance between the sensing elements. FIG. 7 omits components of theforce sensing device 500 and the electronic device in which it isconfigured. For example, FIG. 7 omits the deformable element 514 that isshown between the second sensing element 512 and the third sensingelement 515. Moreover, FIG. 7 omits some details of the sensing elements505, 512, 515 for clarity, such as conductive traces or leads used tocouple the sensing elements (or portions thereof) to other electricalcircuitry.

As noted above, in the force sensing device 500, the first and thirdsensing elements 505, 515 may be drive layers for a capacitive sensingscheme, and the second sensing element 512 may be a sense layer. Inoperation, the first and third sensing elements 505, 515 (also referredto as drive layers 505, 515) may be excited with an electrical signal,such as a substantially sinusoidal signal, a square or edge signal(e.g., a substantially instantaneous transition from a first voltage toa second voltage), or any other appropriate signal. Properties of thesignal, such as frequency, voltage, or amplitude, may be selected toavoid or minimize interference with other electronic circuits of adevice, such as display circuits, processors, antennas, and the like.Because the second sensing element 512 (also referred to as a senselayer) is capacitively coupled to a drive layer, a correspondingelectrical signal may be induced in (or otherwise detected by) the senselayer. For a given electrical signal applied to the drive layers, theinduced electrical signal in the sense layer may be different dependingon the distance between the drive layer and the sense layer. Thus, theforce sensing device 500 (or the associated sensing circuitry) maydetermine the distance between the sense layer and drive layer byanalyzing the signal induced in the sense layer.

The first drive layer 505 may include a conductive material coupled orotherwise applied to a substrate. For example, the first drive layer 505may include a layer of ITO, nanowire (e.g., metallic nanowire, includingsilver or gold nanowire), or any other appropriate material. As shown inFIG. 5, the drive layer 505 is disposed in the light path of the display102 (e.g., it is above the lower stack 508, which produces the lightused to illuminate the display 102). Thus, the conductive material maybe substantially transparent. Even when a substantially transparentmaterial is used, if the material is arranged in a regular pattern, suchas in a grid or columns, it may be visible on the display 102.Accordingly, the conductive material of the first drive layer 505 may besubstantially uniformly distributed (e.g., as a layer, sheet, coating,or other continuous element) on the first drive layer 505 instead ofbeing arranged in a regular pattern. In some cases, the conductivematerial may be a continuous layer covering or extending over an entiresurface of a substrate of the first drive layer 505 (or substantially anentire surface, such as about 80% or more of the surface area of thesubstrate). The layer of conductive material may be configured so thatthere are no borders or edges of the layer positioned within theboundaries of a display in which the force sensing device 500 isincorporated.

The first drive layer 505 may also include a connection element 706 thatis electrically coupled to the conductive material and facilitates thecoupling of the electrical material to other electronic components orcircuitry. The connection element 706 may be formed from or include anymaterial, such as silver, copper, nickel vanadium, or any otherappropriate material. The connection element 706 may form a continuousframe along an outer portion of the first drive layer 505 (as shown), orit may be formed from discontinuous or distinct segments. In some cases,the connection element 706 does not form a frame, but instead may be astrip along one side of the first drive layer 505, for example. Otherconfigurations are also possible. Connection elements 706, such asconductive strips formed on an edge of a drive layer 505 (or any otherconductive substrate, layer, coating, etc.) are discussed herein withrespect to FIGS. 26-29 and 32-40.

The sense layer 512 may include sensing regions 702 formed from (orincluding) a conductive material and arranged in a substantially regularpattern, such as a grid. The sensing regions 702 may be formed from orinclude any appropriate material, such as ITO, metallic nanowire, or thelike.

Each of the sensing regions 702 may act as a discrete area or pixel-likeregion that may be used to determine a distance between the first drivelayer 505 and that particular sensing region. By analyzing all of thesensing regions 702, the force sensing device 500 can detect an amountof an applied force on the cover 303. Moreover, pixelating the senselayer 512 as shown may allow the force sensing device 500 to detectforce with greater accuracy than if a single, uniform sense layer wereused. For example, if a single sense layer were used, it may bedifficult or impossible to tell the difference between a large forceapplied near an edge of the cover 303 and a small force applied near acenter of the cover 303. By using a pixelated sense layer 512, the forcesensing device 500 can account for differences in stiffness among thedifferent regions of the cover 303. Using a pixelated sense layer 512may also allow the force sensing device 500 to determine the location ofan applied force, detect multi-touch inputs (e.g., corresponding tomultiple fingers or styli being applied to the cover 303), or the like.

The second drive layer 515 may include a plurality of drive regions 704.Like the first drive layer 505 and the sensing regions 702 of the senselayer 512, the drive regions 704 may be formed from or include anyappropriate conductive material, such as ITO, metallic nanowire, or thelike.

The drive regions 704 may be arranged in any appropriate pattern ororientation, and may have any appropriate size. For example, the driveregions 704 may be a plurality of substantially rectangular areas ofconductive material, and may be substantially aligned with a column ofsensing regions 702 in the sense layer 512, as shown and described withrespect to FIG. 8. Thus, the drive regions 704 may each overlap multipleones of the sensing regions 702 of the sense layer 512.

Like the first drive layer 505, the drive regions 704 may be excitedwith an electrical signal (e.g., a substantially sinusoidal or edgesignal) that induces a corresponding signal in the sensing regions 702of the sense layer 512 (or that can otherwise be detected by the senselayer 512). Because a single sense layer 512 is used to detect thedistance between it and two different drive layers 505, 515, the forcesensing device 500 needs to differentiate between signals from the firstdrive layer 505 and the second drive layer 515. Accordingly, the signalsfrom the first and second drive layers 505, 515 may have differentfrequencies, amplitudes, phases, or other properties such that thesignals they induce in the sense layer 512 are differentiable from oneanother. More particularly, the signal applied to the first drive layer505 may have a first frequency, and the signal applied to the seconddrive layer 515 may have a second frequency different from the firstfrequency. Alternatively or additionally, the first and second drivelayers 505, 515 may be excited (e.g., with an edge signal) at differenttimes, such that the signal induced in the sense layer 512 can beattributed to one or the other drive layer. For example, sensingcircuitry may alternate between exciting the first and second drivelayers 505, 515. These (or other) techniques may be used so that thedistance between the first drive layer 505 and the sense layer 512 canbe detected independently of the distance between the second drive layer515 and the sense layer 512.

The drive regions 704 may be electrically isolated from one another, orthey may be electrically coupled to one another. In embodiments wherethe drive regions 704 are electrically coupled to one another, all ofthe drive regions 704 may be simultaneously excited by a single signal.

Alternatively, where the drive regions 704 are electrically isolated,they may be driven or excited independently of one another. This may beuseful when not all of the sensing regions 702 are analyzed at a time.More particularly, circuitry associated with the force sensing device500 may cyclically poll subsets of the sensing regions 702. The driveregions 704 may therefore correspond to the polled groups of sensingregions 702, and a signal may be provided to drive regions 704 while thecorresponding group of sensing regions 702 is being polled. This mayhelp to reduce power consumption by the force sensing device 500 when acyclic polling technique is used, as not all of the drive regions 704will be energized when the corresponding sensing regions 702 are notbeing polled.

The drive layers 505, 515 and the sense layer 512 may be distinct layersor components, as shown in FIG. 7, or they may be incorporated intoother layers or components. For example, the first drive layer 505 maybe a conductive material coated on, applied to, or otherwiseincorporated with a polarizing filter that is part of the upper stack304 (FIG. 3A). Indeed, the conductive material of any of the sense anddrive layers may be incorporated on another component or layer of theelectronic device in which it is incorporated. Alternatively, the senseand drive layers may be formed separately, such as by applying aconductive material on substrate such as a flexible circuit material(e.g., polyimide, polyethylene terephthalate, polyether ether ketone, ortransparent conductive polyester), and then incorporating the substrateinto the electronic device.

FIG. 8 is a partial cross-sectional view of the first and second drivelayers 505, 515 and the sense layer 512, viewed along line C-C in FIG.7, illustrating relative sizes and positions of the sensing and driveregions 702, 704 of the force sensing device 500. The first drive layer505 includes a substrate 802, a conductive layer 804, and the connectionelement 706. The substrate 802 may be any appropriate material orcomponent, such as a flexible circuit material, a polarizing filter, orany other material or component of an electronic device or displaystack. The conductive layer 804 may be ITO, a layer of metallic orconductive nanowire, or any other appropriate material, as describedabove. The conductive layer 804 may be a continuous sheet (e.g., havinga single expanse of conductive material, rather than a segmented orpixelated configuration) that overlaps multiple sense regions 702. Theconnection element 706 may be a conductive material such as copper,silver, nickel vanadium, or the like.

The sense layer 512 may include a substrate 806, which may be anyappropriate material or component, such as flexible circuit material,and the sensing regions 702. As described above, the sensing regions 702may be formed from or include any appropriate material, including ITO,conductive nanowire, or the like.

The second drive layer 515 may include a substrate 808, which may be anyappropriate material or component, such as flexible circuit material,and the drive regions 704. The drive regions 704 and the sensing regions702 of the sense layer 512 may be sized and positioned relative to oneanother such that the sensing regions 702 shield the drive regions 704from sources of interference such as the first drive layer 505. Forexample, the drive regions 704 may be substantially the same width as,or narrower than, the sensing regions 702, and may be vertically alignedwith the sensing regions 702 (with the positional terms being relativeto the orientation of the layers in FIG. 8). In this way, the conductivematerial of the sensing regions 702 may substantially shield the driveregions 704 from the first drive layer 505 or other potential sources ofinterference above the sense layer 512. Some portions of the driveregions 704 may not be directly covered by a sensing region 702.However, the unshielded area of the substantially rectangular driveregions 704 is significantly less than would be present if the seconddrive layer 515 were a single continuous sheet of conductive material,such as that on the first drive layer 505.

FIG. 8 shows the sensing regions 702 and the drive regions 704 extendingabove the surface of their respective substrates. This is merely oneexample configuration, however. Indeed, the sensing and drive regions702, 704 may be substantially flush with or recessed in their respectivesubstrates.

FIG. 9 shows the sense layer 512 with an example distribution of sensingregions 702. FIG. 9 also shows conductive paths 902 that mayelectrically couple the sensing regions 702 to other electroniccomponents or circuits. The conductive paths 902 may be any appropriatematerial and may be formed in any appropriate way. For example, they maybe formed from ITO applied using a photolithography technique. Othermaterials and techniques are also contemplated. In embodiments where thesensing regions 702 are independently polled to provide unique forcevalues for a particular display location (as shown in FIG. 9), eachsensing region 702 may be connected to a unique conductive path 902. Inembodiments where multiple sensing regions 702 are polled or monitoredas a single unit, those sensing regions 702 may share or be connected toa common conductive path 902 (not shown). The pattern of sensing regions702 and conductive paths 902 shown in FIG. 9 is merely one example of asuitable configuration, and other configurations, including the numberand arrangement of the sensing regions 702 and conductive paths 902, arealso contemplated.

FIG. 10A shows the first drive layer 505, illustrating an exampleconfiguration of an electrical connection to the conductive layer 804 ofthe first drive layer 505 via the connection element 706 (e.g., aconductive strip or border around the first drive layer 505). Inparticular, FIG. 10A illustrates a pair of connector segments 1002positioned proximate the connection element 706. Each connector segment1002 may be formed from or include an electrical conductor that iselectrically connected to a signal generator or other electroniccircuitry. For example, the connector segment 1002 may be formed from aflexible circuit material with a metallic or conductive material (e.g.,copper, gold, ITO) disposed thereon. In some cases, the connectorsegment 1002 may be formed substantially entirely of conductivematerial, such as when the connector segment 1002 is a strip of copper,silver, or any other metal or conductive material.

A conductive joining material 1004 may be deposited over connectorsegments 1002 and a portion of the connection element 706 such that anelectrical connection is formed between the connector segments 1002 andthe connection element 706. The conductive material may be anyappropriate material, such as silver, gold, copper, conductiveadhesives, or the like.

As noted above, the connection element 706 is electrically connected tothe conductive layer 804. Accordingly, drive signals can be applied fromthe connector segments 1002 to the conductive layer 804. In some cases,more or fewer connector segments 1002 may be used to electrically couplecircuitry to the conductive layer 804, or the connector segments 1002may be positioned at different locations around the drive layer 505,such as along opposite edges of the drive layer 505.

FIG. 10B shows the first drive layer 505, illustrating another exampleconfiguration of an electrical connection to the conductive layer 804 ofthe first drive layer 505. As shown, the first drive layer 505 does notinclude the connection element 706. In this example, instead ofconnecting to the conductive layer 804 via the connection element 706(as shown in FIG. 10A), the connector segments 1006 connect to theconductive layer 804 via a conductive adhesive 1008. Like the connectorsegments 1002 (FIG. 10A), the connector segments 1006 may be formed fromor include an electrical conductor that is electrically connected to asignal generator or other electronic circuitry. The connector segments1006 may be electrically and physically coupled to the conductive layer804 via the conductive adhesive 1008, which may be disposed betweenoverlapping portions of the connector segments 1006 and the conductivelayer 804. FIG. 10B illustrates an example embodiment where twoconnector segments 1006 couple to opposite sides of the first drivelayer 505. Other configurations, including different numbers, sizes,shapes, and coupling locations of the connector segments 1006 are alsocontemplated. For example, in some cases, only one connector segment1006 is used. In other cases, four connector segments 1006 are arrangedaround the first drive layer 505 (e.g., with one connector segment 1006on each side of the first drive layer 505).

FIG. 11 shows the second drive layer 515, with an example distributionof drive regions 704. FIG. 11 also shows conductive paths 1102 that mayelectrically couple the drive regions 704 to other electronic componentsor circuits. The conductive paths 1102 may be any appropriate materialand may be formed in any appropriate way. For example, they may beformed from ITO applied using a photolithography technique. Othermaterials and techniques are also contemplated. In embodiments where thedrive regions 704 are independently driven or excited, as discussedabove with respect to FIG. 8, each drive region 704 may be connected toa unique conductive path 1102. In embodiments where multiple driveregions 704 are driven or excited together (e.g., a signal is applied tomultiple drive regions 704 simultaneously), those drive regions 704 mayshare or be connected to a common conductive path (not shown). Thepattern of drive regions 704 and conductive paths 1102 shown in FIG. 11is merely one example of a suitable configuration, and otherconfigurations, including the number and arrangement of the driveregions 704 and conductive paths 1102, are also contemplated.

FIG. 12 is a partial cross-sectional view of an example force sensingdevice 1200 that may be incorporated in an electronic device (e.g., thedevices 100, 200), depicting an area similar to the area 301 in FIG. 3A.The cover 303 and the housing 104 are omitted for clarity. While theforce sensing device 1200 is similar to the force sensing device 500,the force sensing device 1200 has a different number and arrangement ofsensing elements within the electronic device, as described herein.

The force sensing device 1200 includes an upper stack 1204, similar tothe upper stack 304, which may include one or more layers or componentsof a display, including a liquid crystal matrix, light emitting diodes(LEDs), light guides, filters (e.g., polarizing filters), diffusers,electrodes, or the like. The upper stack 1204 may be configured to flexor be capable of flexing in response to an applied force on the forcesensing device 1200.

A lower stack 1208 may be disposed below the upper stack 1204 andseparated from the upper stack 1204 by an air gap 1206. The lower stack1208 may include a frame member 1207 (similar to the frame member 309),an optical stack 1213 (similar to the optical stack 315 describedabove), and any other appropriate components, such as a light source. Asdescribed with respect to the assembly 300, the air gap 1206 may be anyappropriate thickness, such as 25 to 100 microns. In embodiments wherethe force sensing device 1200 does not include a display or does notprovide display functionality, the lower stack 1208 (as well as theupper stack 1204) may include different components or be omitted.

A first sensing element 1209 is coupled to the lower stack 1208. Thefirst sensing element 1209 may be a capacitive sensing element that isconfigured to capacitively couple with another capacitive sensingelement. For example, the first sensing element 1209 may be a drivelayer that is capacitively coupled to a sense layer (e.g., the secondsensing element 1215, described below) that facilitates detection of adistance between the sense and drive layers using mutual capacitance. Asanother example, the first sensing element 1209 may be a sense layerinstead of a drive layer. As yet another example, the first sensingelement 1209 may be configured to capacitively couple to a ground layerand facilitate detection of a distance between itself and the groundlayer using self-capacitance. As yet another example, the first sensingelement 1209 may be a ground layer that capacitively couples to a senselayer.

The first sensing element 1209 may be formed from or include anyappropriate material, such as ITO traces disposed on a flexiblesubstrate, and may be coupled to the lower stack 1208 in any appropriateway, such as with a PSA or HSA, or patterned directly onto the lowerstack 1208. Because the first sensing element 1209 is below the lowerstack 1208, the frame member 1207 of the lower stack 1208 may be formedfrom a conductive material, such as a metal. More particularly, becausethe frame member 1207 is not between the first sensing element 1209 anda second sensing element 1215 (discussed below), the frame member 1207may not shield or otherwise negatively interfere with the capacitivecoupling between the first and second sensing elements 1209, 1215.Accordingly, more materials may be suitable for use in the frame member1207, and the frame member 1207 may define a continuous layer or panel,rather than having an opening therein to avoid undesirable shielding orinterference.

An air gap 1210 and a deformable element 1214 may be disposed betweenthe first sensing element 1209 and a second sensing element 1215. Theair gap 1210 and the deformable element 1214 correspond to the air gap510 and deformable element 514, and may have similar compositions,structures, dimensions, and functions.

The second sensing element 1215 may be capacitively coupled to the firstsensing element 1209, and together these components may form acapacitive sensor 1218 that spans the air gap 1210 and the deformableelement 1214 to detect deformation of these layers. The second sensingelement 1215 may be a sense layer, a drive layer, or a ground layer,depending on the principle of operation of the capacitive sensor 1218and/or the configuration of the first sensing element 1209.

The second sensing element 1215 may be coupled to a base structure 1216,which may be a frame, a bracket, a circuit board, a battery, an interiorwall of a housing or enclosure, or the like, as described above withrespect to the base structure 516 of FIG. 5.

FIG. 13 is an example force versus deflection curve illustrating how theforce sensing device 1200 in FIG. 12 deflects in response to a forceinput applied (directly or indirectly) to the upper stack 1204. Theforce response is similar to that shown in FIG. 4, with a first profileextending from point 401 to point 402 (corresponding to collapse of theair gaps 1206 and 1210) and a second profile extending from point 402 topoint 404 (corresponding to deformation of the deformable element 1214).

As noted above, the force sensing device 1200 has one capacitive sensor1218 formed by the first and second sensing elements 1209, 1215. Thefirst and second sensing elements 1209, 1215 span the air gap 1210 andthe deformable element 1214, but do not span the air gap 1206. Thus, thecapacitive sensor 1218 does not detect deflection of the upper stack1204 that causes the air gap 1206 to collapse (corresponding to line1302 in FIG. 13), but does detect deflection that causes the air gap1210 to collapse and the deformable element 1214 to be deformed(corresponding to line 1304 in FIG. 13). Accordingly, the collapse ofthe air gap 1206 is decoupled from the collapse of the air gap 1210, anda force detected using the capacitive sensor 1218 of the force sensingdevice 1200 corresponds to the force required to collapse the air gap1210.

Because the capacitive sensor 1218 spans both the air gap 1210 and thedeformable element 1214, sensing circuitry coupled to the first andsecond sensing elements 1209, 1215 may be configured to algorithmicallydetermine when the air gap 1210 has fully collapsed. For example, thesensing circuitry may monitor a rate of change of deformation (e.g., aslope of the force versus deflection curve) as a force is applied. Ifthe slope satisfies a first condition (e.g., it is constant or it isbelow a threshold value), the sensing circuitry may determine that onlythe air gap 1210 is being or has been collapsed, and may apply a firstforce-deflection correlation. If the slope satisfies a second condition(e.g., it is increasing or it is above the threshold value), the sensingcircuitry may determine that the air gap 1210 has been fully collapsedand the deformable element 1214 is about to be deformed or has been atleast partially deformed. In the latter case, the sensing circuitry mayapply a second force-deflection correlation to determine a value of theapplied force.

FIG. 14 is a partial cross-sectional view of an example force sensingdevice 1400 that may be incorporated in an electronic device (e.g., thedevices 100, 200), depicting an area similar to the area 301 in FIG. 3A.In this example, the force sensing device 1400 is the same as the forcesensing device 1200 except that the first sensing element 1209 iscoupled to the upper stack 1204 such that the capacitive sensor 1402formed by the first and second sensing elements 1209, 1215 spans boththe air gap 1206 and the air gap 1210. Accordingly, as illustrated inthe force versus deflection curve in FIG. 15, the capacitive sensor 1402detects deflection of the upper stack 1204 from point 401 to point 404(corresponding to line 1502). Moreover, as described herein, sensingcircuitry may be configured to algorithmically determine when the airgap 1210 and optionally the air gap 1206 have fully collapsed in orderto apply an appropriate force-deflection correlation.

Whereas in FIG. 12, the frame member 1207 was not between the first andsecond sensing elements 1209, 1215, in FIG. 14 the frame member 1207 isbetween the first and second sensing elements 1209, 1215. Accordingly,the frame member 1207 may be formed from a dielectric material or mayhave an opening in which a dielectric material is positioned such thatthe frame member 1207 does not shield or otherwise interfere with thesensing elements 1209, 1215.

FIG. 16 is a partial cross-sectional view of an example force sensingdevice 1600 that may be incorporated in an electronic device (e.g., thedevices 100, 200), depicting an area similar to the area 301 in FIG. 3A.In this example, the force sensing device 1600 includes an upper stack1604 (corresponding to the upper stack 1204), a first sensing element1605 (corresponding to the first sensing element 1209), an air gap 1606(corresponding to the air gap 1206), a lower stack 1608 (correspondingto the lower stack 1208), a deformable element 1610, an air gap 1615, asecond sensing element 1614, and a base structure 1620 (corresponding tothe base structure 1216). The lower stack 1608 may include an opticalstack 1617 and a frame member 1607 supporting the optical stack 1617 andcoupling the lower stack 1608 to the upper stack 1604. Because the framemember 1607 is between the first and second sensing elements 1605, 1614(similar to the configuration in the force sensing device 500, FIG. 5),the frame member 1607 may be formed from or include a dielectricmaterial, such as a dielectric material disposed in an opening in theframe member 1607.

The first and second sensing elements 1605, 1614 form a capacitivesensor 1619 that spans both the air gap 1606 and the air gap 1615. Thus,like in the force sensing device 1400, the capacitive sensor 1619detects deformation that corresponds to the collapse of both air gaps1606, 1615, as well as the deformable element 1610. Accordingly, asillustrated in the force versus deflection curve in FIG. 17, thecapacitive sensor 1619 detects deflection of the upper stack 1604 frompoint 401 to point 404, corresponding to line 1702.

The force sensing device 1600 also includes a contact sensor that isconfigured to detect contact between the upper and lower stacks. Asshown in FIG. 16, the contact sensor is integrated with the deformableelement 1610 and the second sensing element 1614. For example, thedeformable element 1610 may include protrusions 1611 extending from abase portion of the deformable element 1610. The protrusions 1611 mayinclude a sense element 1612 that is configured to be sensed orotherwise detected by a contact sensing region (e.g., a contact sensingregion 1616, discussed herein) when the air gap 1615 has been fullycollapsed and the deformable element 1610 contacts the second sensingelement 1614. As shown in FIG. 16, the sense elements 1612 are disposedat free ends of the protrusions 1611.

The sense elements 1612 may be formed from any appropriate material andmay have any appropriate size and shape. These properties, as well asany other property of the sense elements 1612, may be selected based onthe principle of operation of the contact sensor. For example, if acontact sensing region 1616 is a capacitive sensor, the sense elements1612 may be a conductive material, and/or a dielectric material. Asuitable dielectric material may have a dielectric constant (or relativepermittivity) greater than about 3.9 (e.g., a high-k dielectricmaterial). Where the contact sensing region 1616 is a continuity sensor,the sense elements 1612 may be a conductive material such as carbon,metal, or the like.

The sense elements 1612 may be incorporated in the deformable element1610 in any appropriate way. For example, the sense elements 1612 may beco-molded with the deformable element 1610. In another example, thesense elements 1612 may be deposited on the deformable element 1610. Forexample, a layer or layers of metal (or any other appropriate material)may be deposited on free ends of the protrusions 1611. In yet anotherexample, the deformable element 1610 may be formed of a material that isitself configured to be sensed by a corresponding contact sensing region1616, and thus discrete sense elements 1612 may not be used. Forexample, the material may be a silicone or other elastomer withconductive particles, such as carbon, embedded therein. Other materialsand techniques for integrating the materials with the deformable element1610 are also contemplated.

The contact sensor of the force sensing device 1600 also includescontact sensing regions 1616 that are configured to detect the senseelements 1612 to determine when the air gap 1615 has been fullycollapsed and the deformable element 1610 has begun to be compressed.The contact sensing regions 1616 may be configured to detect the senseelements 1612 in any appropriate way. For example, the contact sensingregions 1616 may include capacitive sensing components that areconfigured to detect a change in capacitance caused by the proximity ofthe sense elements 1612 to the contact sensing regions 1616. As anotherexample, the contact sensing regions 1616 may include electricalswitches that are configured to detect a closed circuit when aconductive sense element 1612 contacts the electrical switches.

The contact sensing regions 1616 may be integrated with the secondsensing element 1614. For example, the contact sensing regions 1616 forthe contact sensor and sensing regions for the capacitive force sensor1619 may be patterned on or otherwise incorporated in the samesubstrate. As another example, the contact sensing regions 1616 may bedisposed on top of the second sensing element 1614. For example, contactsensing regions 1616 comprising electrical contacts, capacitive sensingcomponents, or the like may be placed on top of and optionally adheredto the second sensing element 1614.

Similar to the force sensing device 1400 in FIG. 14, the force sensingdevice 1600 forms a capacitive sensor 1619 that spans both the air gap1615 and the deformable element 1610, and thus the capacitive sensor1619 exhibits a force response curve (shown in FIG. 17) that extendsfrom point 401 to point 404 (corresponding to line 1702). However, thecapacitive sensor 1619 may not provide a discrete indication when theforce sensing device 1600 is operating in the first force profile (e.g.,from point 401 to point 402) or the second force profile (e.g., frompoint 402 to point 404). The contact sensor of the force sensing device1600 provides this indication, allowing sensing circuitry to apply anappropriate force-deflection correlation. For example, before the airgap 1615 is fully collapsed and before the contact sensor indicates acontact event (corresponding to point 1704 in FIG. 17), the sensingcircuitry may apply a first force-deflection correlation correspondingto the collapse of the air gap 1615 (from point 401 to point 402). Afterthe air gap 1615 has fully collapsed, as detected and indicated by asignal from the contact sensor (at point 1704), the sensing circuitrymay apply a second force-deflection correlation corresponding tocompression of the deformable element 1610 (e.g., from point 402 topoint 404).

While FIG. 16 illustrates an embodiment where the first sensing element1605 is disposed on the upper stack 1604, and thus includes the air gap1606 in the space between the first and second sensing elements 1605,1614, other configurations are possible. For example, the first sensingelement 1605 may be disposed on the lower stack 1608 on the oppositeside of the air gap 1606, or it may be disposed between the lower stack1608 and the deformable element 1610. Regardless of where the first andsecond sensing elements 1605, 1614 are located in the force sensingdevice 1600, an air gap, a deformable element, and a contact sensor maybe disposed between them. Moreover, FIG. 16 illustrates the deformableelement 1610 positioned on the lower stack 1608, with the protrusions1611 extending towards the base structure 1620, and illustrates thecontact sensing regions 1616 positioned on the base structure 1620. Inother embodiments, the relative positioning of these components may beexchanged, such that the deformable element 1610 is positioned on thebase structure 1620 with the protrusions 1611 extending towards thelower stack 1608, and the sensing regions 1616 are positioned on thelower stack 1608. It will be understood that this modification mayproduce an equivalent result at least with respect to the operation ofthe deformable element 1610 and the contact sensing regions 1616.

FIG. 18A is an expanded view of the area 1800 in FIG. 16, showing anexample configuration of the protrusions 1611, sense elements 1612, andcontact sensing regions 1616 that may form the contact sensor in FIG.16. The second sensing element 1614 may include sensing regions 1810,such as capacitive plates or leads that capacitively couple to a groundor drive layer, as well as the contact sensing regions 1616. The contactsensing region 1616 in FIG. 18A includes leads 1802, 1804, 1806, and1808. The leads may be any appropriate material (such as traces ofconductive material (e.g., metal, carbon, ITO), wires, plates, pads, orthe like), and may be coupled to appropriate circuitry for detectingcontact with or proximity to the sense element 1612. For example, theleads may be capacitive elements that facilitate detection of a changein capacitance resulting from the sense element 1612 being brought intocontact with or proximity to the leads. As another example, the leadsmay be electrical contacts that facilitate detection of a closed circuitbetween two or more contacts.

FIG. 18B illustrates the area 1800 in FIG. 16 when the air gap 1615 hasbeen fully collapsed and the deformable element 1610 is in contact withthe second sensing element 1614. As shown, the proximity or contactbetween the sense element 1612 and the leads 1802, 1804, 1806, and 1808results in detection by corresponding pairs of the leads 1802, 1804,1806, and 1808. While FIGS. 18A-18B illustrate four leads, this ismerely an example, and more or fewer leads may be used. Moreover, therelative sizes of the contact sensing region 1616, the sense element1612, and the leads 1802, 1804, 1806, and 1808 are merely exemplary, andmay be selected based on various factors and considerations. Forexample, the contact sensing regions 1616 may be large enough toaccommodate misalignments between the deformable elements 1610 and thecontact sensing regions 1616. Thus, even if the centers of theprotrusions 1611 and the contact sensing regions 1616 do not line upexactly, the contact sensor will still effectively detect when the airgap 1615 has fully collapsed.

FIG. 19 shows an example of the deformable element 1610, or a portionthereof. The deformable element 1610 comprises an array of protrusions1611 extending from a base surface 1900. The protrusions 1611 may beintegrally formed with the base surface 1900. For example, thedeformable element 1610 may be molded (e.g., injection molded) as aunitary, monolithic component of a substantially uniform composition. Asnoted above, the sense elements 1612 may be co-molded with thedeformable element 1610 or they may be applied (e.g., adhered, coated,or deposited) to or on the protrusions 1611 after the deformable element1610 is formed. In either case, the sense elements 1612 may be at leastpartially embedded in the protrusions 1611. Other techniques forsecuring the sense elements 1612 to the protrusions 1611 are alsocontemplated. It will be understood that the protrusions 1611 are forillustrative purposes, and are not necessarily to scale relative to thesize of the base surface 1900 or any other components depicted in thefigures.

FIG. 20 shows an example of the second sensing element 1614, or aportion thereof, that includes both sensing regions 1810 (indicated byplain squares) and contact sensing regions 1616 (indicated bycross-hatched squares), and which may be used in conjunction with thedeformable element 1610 shown in FIG. 19. Both the sensing regions 1810and the contact sensing regions 1616 may be formed on the same substrate2000 (e.g., a flexible circuit material), and may include conductivetraces, such as metals, carbon, ITO, or the like.

In the examples shown in FIGS. 19 and 20, each protrusion 1611 includesa sense element 1612 and corresponds to a contact sensing region 1616 onthe second sensing element 1614. This need not be the case, however, asthe considerations that determine the amount, arrangement, anddistribution of the protrusions 1611 that provide a suitable resistanceto compression may be different than the considerations driving theamount, arrangement, and distribution of contact sensing regions. Forexample, in some implementations, some of the protrusions 1611 do notcorrespond to contact sensing regions 1616. In such cases, theprotrusions 1611 that do not correspond to contact sensing regions 1616may omit the sense element 1612, but may be formed or shaped to ensurethat all of the protrusions 1611 have substantially the same height.Alternatively, all of the protrusions 1611 may include a sense element1612 regardless of whether they all correspond to a contact sensingregion 1616. This may ensure that all of the protrusions have the sameheight and contact an opposing surface at substantially the same time.

FIG. 21A is a cross-sectional view of an example contact sensor 2100,showing a section similar to those shown in FIGS. 18A-18B. Whereas thecontact sensor formed by the protrusions 1611 and the contact sensingregions 1616 shown in FIGS. 18A-18B places the sensing component and thesensed component on opposite sides of the air gap 1615, the contactsensor 2100 is configured such that both the sensed and sensingcomponents can be disposed on one side of an air gap.

The contact sensor 2100 includes a deformable protrusion 2102, which maybe formed of any appropriate deformable material, such as silicone,polyurethane foam, rubber, gel, or the like. A sense element 2104 may beincorporated with the protrusion 2102. For example, the sense element2104 may be placed within a cavity 2106 or other internal region of theprotrusion 2102. The sense element 2104 may also be embedded in thematerial of the protrusion 2102 (e.g., via co-molding or insertmolding). Like the sense element 1612, the sense element 2104 may beformed from or include any appropriate material, such as a dielectricmaterial and/or a conductive material.

The contact sensor 2100 also includes leads 2110 in an adjacent layer2108. The adjacent layer 2108 may be a sensing element, such as thesensing element 1614, in or on which the leads 2110 are incorporated.Alternatively, the adjacent layer 2108 may be dedicated to containingthe leads 2110. Like the leads 1802, 1804, 1806, and 1808 in FIGS.18A-18B, the leads 2110 may be configured to act as capacitive elements(e.g., capacitive plates to capacitively couple to and detect theproximity of the sense element 2104), contacts for a continuity sensor,or the like. Moreover, the leads 2110 may be formed from or include anyappropriate material, such as traces of conductive material (e.g.,metal, carbon, ITO), wires, plates, pads, or the like. The leads 2110may be coupled to appropriate circuitry for detecting contact with orproximity to the sense element 2104.

Where the contact sensor 2100 is a capacitive sensor, physical contactbetween the leads 2110 and the sense element 2104 may not be necessaryto detect contact between the protrusion 2102 and another component.Rather, when the protrusion 2102 contacts another component (e.g.,because an adjacent air gap has been fully collapsed), the leads 2110,along with associated circuitry, may detect the change in distancebetween the sense element 2104 and the leads 2110, thereby triggeringthe contact sensor 2100. In such cases, the cavity 2106 may be filledwith a deformable material, such as silicone, thereby encapsulating thesense element 2104.

FIG. 21B illustrates the contact sensor 2100 after the protrusion 2102has been deformed by a layer 2112 forming an opposite side of an air gapin which the protrusion 2102 has been disposed. As shown, the senseelement 2104 has been brought into contact with the leads 2110, thustriggering the contact sensor 2100. It may not be necessary for thesense element 2104 to actually contact the leads 2110, however, in orderfor the contact sensor 2100 to be triggered. For example, where theleads 2110 are configured as capacitive sensors (or any other type ofsensor capable of detecting a change in distance between it and anotherobject), the contact sensor 2100 may be triggered by any detectablechange in distance between the sense element 2104 and the leads 2110caused by the layer 2112 deforming or otherwise contacting theprotrusion 2102.

FIG. 22A is a cross-sectional view of an example contact sensor 2200,showing a section similar to those shown in FIGS. 18A-18B. Whereas thecontact sensor formed by the protrusions 1611 and the contact sensingregions 1616 shown in FIGS. 18A-18B places the sensing component and thesensed component on opposite sides of the air gap 1615, the contactsensor 2200 is configured such that both the sensed and sensingcomponents can be disposed on one side of an air gap.

The contact sensor 2200 includes a deformable protrusion 2202, which maybe formed of any appropriate deformable material, such as silicone,polyurethane foam, rubber, gel, or the like. A sense element 2204 may bedisposed over the protrusion 2202. For example, a material may bedisposed over at least a portion of the protrusion 2202, such as bycoating, deposition (e.g., physical vapor deposition or chemical vapordeposition), or any other appropriate mechanism. The contact sensor 2200also includes leads 2208 in a layer 2206 that is proximate theprotrusion 2202.

The leads 2208 may be configured to act as capacitive elements thatcapacitively couple to the sense element 2204, thereby sensing changesin distance from the leads 2208 to the sense element 2204. Accordingly,the sense element 2204 may be formed from or include a conductivematerial, a dielectric material (e.g., a high-k dielectric material), orany other appropriate material that may be capacitively coupled to andsensed by the leads 2208.

FIG. 22B illustrates the contact sensor 2200 after the protrusion 2202has been deformed by a layer 2210 forming an opposite side of an air gapin which the protrusion 2202 is disposed. As shown, the sense element2204 has been brought into closer proximity to the leads 2208, thustriggering the contact sensor 2200.

The contact sensors 2100, 2200 may be used instead of or in conjunctionwith the contact sensors described with respect to FIGS. 18A-20. Forexample, instead of the protrusions 1611 and the sensing regions 1616,which together form a contact sensor to detect contact with thedeformable element 1610, the deformable element 1610 may include aplurality of contact sensors 2100 or 2200 that serve the same or asimilar function.

The contact sensing systems described herein may be applied between anyof the layers or components of a force sensing device. For example,while FIG. 16 depicts a contact sensor to detect when the air gap 1615has collapsed, a contact sensor may also or instead be configured todetect contact when the air gap 1606 has collapsed. In some cases,multiple air gaps in a stack of a force sensing device may include acontact sensor. By providing additional contact sensors in this manner,an electronic device may determine which layers have been or are beingdeflected, and may therefore apply force-deflection correlations thatare tailored for the particular layer or layers that are beingdeflected. By providing a distinct force-deflection correlation for eachof multiple layers, an amount of force applied to a surface may bedetermined with a high degree of accuracy.

The deformable elements described in each of the foregoing examplesabove may have different thicknesses and/or different protrusion heightsin different areas when the deformable element is in an undeformedstate. For example, the base structures and/or the upper or lower stacksof the force sensing devices (or any other layer of a force sensingdevice) may not have uniformly planar surfaces. Accordingly, in order toprovide a relatively constant air gap size across the air gap, thedeformable elements may have different thicknesses in different areas.For example, protrusions may be larger in some areas to account for agreater distance between a layer or stack (e.g., the lower stack 308)and a base structure (e.g., the base structure or layer 316).

In some cases, input surfaces may not deflect uniformly across theentire input surface area. For example, a force applied near an edge ofthe cover 303 (e.g., close to the joint between the housing 104 and thecover 303) may cause less deflection of the cover 303 (and hence theupper and lower stacks 304, 308) than a force of the same magnitude thatis applied in the center of the cover 303. Accordingly, the deformableelements may be thicker in areas where less deformation is expected(e.g., around the edges or perimeter of the cover 303) so that thedeformable element begins to be compressed at substantially the samemagnitude of force regardless of where on the input surface the force isapplied.

FIG. 23A is a cross-sectional view of an embodiment of the device 100,viewed along line A-A in FIG. 1, showing an assembly 2300 that mayprovide display, touch sensing, and/or force sensing functionality tothe device 100, or may be integrated with other components to providesuch functionality. As shown in FIG. 23A, the device 100 includes forcesensing system in the assembly 2300, similar to the sensors describedabove with respect to FIGS. 5-22, as well as a sensor 2302 (FIG. 23B)positioned between the housing 104 and the cover 303. The sensor 2302works in conjunction with the sensing elements in the assembly 2300 todetermine an amount of deflection of, and thus an amount of forceapplied to, the cover 303.

The assembly 2300 includes the upper and lower stacks 304, 308, the airgaps 306, 310, and the deformable element 314, all of which aredescribed above with respect to FIGS. 3A-3E. The assembly 2300 alsoincludes a first sensing element 2304 positioned on a first side of(e.g., above) the deformable element 314 and a second sensing element2306 positioned on a second side of (e.g., below) the deformable element314. Together, the first and second sensing elements 2304, 2306 may bereferred to as a force sensor.

The first and second sensing elements 2304, 2306 may be similar to anyof the sensing elements described herein. For example, the first sensingelement 2304 may be a capacitive drive layer, and the second sensingelement 2306 may be a capacitive sense layer that is capacitivelycoupled to the drive layer. The first and second sensing elements 2304,2306 and associated circuitry may detect an amount of deformation ordeflection of the deformable element 314, and thus determine an amountof force applied to the cover 303. While the assembly 2300 shows thefirst and second sensing elements 2304, 2306 positioned on oppositesides of the deformable element 314, other configurations are alsopossible. For example, the first sensing element 2304 may be disposed onthe bottom of the frame member 309, on (or in) the upper stack, or thelike. In some cases, any of the force sensing devices described herein,such those shown and described with respect to FIG. 5, 12, 14, or 16,may be used in the assembly 2300.

In addition to the force sensor in the assembly 2300, the device 100 mayinclude a sensor 2302 disposed between the housing 104 and the cover303. The sensor 2302 may include a compliant material that can deflector deform in response to an applied force on the cover 303. The sensor2302, along with associated sensing circuitry, may be able to detect anamount of deflection of the cover 303 in response to an applied force,and, in conjunction with the sensing elements 2304, 2306 in the assembly2300, determine an amount of force applied to the cover 303.

FIG. 23B shows an exploded view of the area 2308 in FIG. 23A, showingdetails of the sensor 2302. The sensor 2302 may be positioned betweenthe ledge 307 of the housing 104 and a portion of the cover 303 suchthat when a force is applied to the cover 303, the sensor 2302 ispressed between the ledge 307 and the portion of the cover 303, thusdeforming the sensor 2302. The geometry of the ledge 307 and the cover303 in FIG. 23B are merely exemplary, and different embodiments of thehousing 104 and the cover 303 may have shapes, geometries, and/orfeatures that are different from those shown in FIG. 23B.

The sensor 2302 includes a deformable portion 2310. The deformableportion 2310 may be formed from or include any appropriate material,such as silicone, polyurethane foam, rubber, gels, elastomers, or thelike. In some cases, the deformable portion 2310 may have adhesiveproperties, such that the sensor 2302 retains the cover 303 to thehousing 104.

The sensor 2302 also includes a first sensing element 2312 and a secondsensing element 2314. The first and second sensing elements 2312, 2314may be positioned on opposite sides of the deformable portion 2310(e.g., a top and bottom, as shown in FIG. 23B). The first and secondsensing elements 2312, 2314 may form a capacitive sensor, in which caseone of the first or second sensing element 2312, 2314 may be acapacitive drive layer, and the other may be a capacitive sense layer.The capacitive sensor may detect an amount of deformation of thedeformable portion 2310, and thus facilitate detection of an amount ofapplied force, as discussed herein. In some cases, the sensor 2302 maybe a resistive sensor (or any other appropriate sensor), in which casethe first and second sensing elements 2312, 2314 may be omitted orsubstituted with other components.

When a force is applied to the cover 303, the deformable portion 2310 ofthe sensor 2302 may deflect or deform such that the first and secondsensing elements 2312, 2314 are brought closer together. The first andsecond sensing elements 2312, 2314 and associated circuitry maydetermine the amount of deformation and correlate it with an amount offorce applied to the cover 303. As a certain amount of applied force isreached, however, the deformable portion 2310 may reach a maximumdeformation, where greater applied forces may not result in furtherdeformation of the deformable portion 2310. In some cases, it may bedesirable to detect applied forces greater than this amount, however.Accordingly, the sensor 2302 and the sensing elements in the assembly2300 may sense different ranges of applied forces.

For example, the sensor 2302 may be configured to determine forcesspanning from no applied force to an amount of force that results in thecollapse of the air gaps 306 and 310 in FIG. 23A. Up until that point,the sensor in the assembly 2300 (formed by the first and second sensingelements 2304, 2306) may not detect any force, as the lower stack 308had not yet been brought into contact with the deformable element 314.Once the lower stack 308 contacts the deformable element 314, increasingamounts of force may be determined by the sensing elements 2304, 2306 inthe assembly 2300.

The first and second sensing elements 2312, 2314 may be formed from orinclude any appropriate material, such as metals, ITO, or the like.Moreover, the first and second sensing elements 2312, 2314 may beapplied to or otherwise incorporated with the deformable portion 2310 inany appropriate manner. For example, the first and second sensingelements 2312, 2314 may be or may include conductive sheets (e.g.,copper, silver, or gold) embedded in, positioned on, or otherwiseintegrated with the deformable portion 2310. As another example, thefirst and second sensing elements 2312, 2314 may be ITO that isdeposited on the deformable portion 2310.

In some cases, either or both of the first and second sensing elements2312, 2314 may not be integrated with the deformable material 2310, butrather may be separate components. For example, the first and/or secondsensing elements 2312, 2314 may be layers of material (e.g., flexiblecircuit material) with conductive materials disposed thereon. The layersmay be positioned between the deformable portion 2310 and the cover 303,and/or between the deformable portion 2310 and the housing 104, and maybe bonded or otherwise adhered to those components. As another example,the first and/or second sensing elements 2312, 2314 may be patterneddirectly on the cover 303 and/or the housing 104. For example, ITO,conductive nanowires, or any other appropriate material, may be formeddirectly on the portions of the cover 303 and the housing 104 that areopposite each other when the device 100 is in its assembledconfiguration. Any combinations of the foregoing examples may be used tointegrate the first and/or second sensing elements 2312, 2314 with thedevice 100.

FIG. 24 is an example force versus deflection curve illustrating how thecover 303 of the device illustrated in FIG. 23A deflects in response toa force input applied thereto. The force response is similar to thatshown in FIG. 4, with a first profile from point 401 to point 402(corresponding to collapse of the air gaps 306 and 310) and a secondprofile from point 402 to point 404 (corresponding to deformation of thedeformable element 314). The sensor 2302 may detect deformation of theair gaps 306, 310, as indicated by the line 2402 in FIG. 24, while theforce sensor in the assembly 2300 detects deformation of the deformableelement 314, as indicated by line 2404. While the lines 2402, 2404 areshown as non-overlapping, this may not be the case. For example, thesensor 2302 may continue to deflect and thus provide meaningful forceinformation even after the air gaps 306, 310 have collapsed. In suchcases, sensing circuitry associated with the sensors may process theinformation from both sensors to determine an amount of applied force.

FIG. 25 shows a portion of the sensor 2302 as viewed through the cover303 of the device. The illustrated portion of the sensor 2302corresponds to a corner portion of the sensor 2302. The sensor 2302includes first drive regions 2502 each electrically coupled together(e.g., via conductors 2503) and second drive regions 2504 eachelectrically coupled together (e.g., via conductors 2505). The first andsecond drive regions 2502, 2504 may together form the second sensingelement 2314 shown in FIG. 23B, and may be driven or excited with asignal. As shown, the first and second drive regions 2502, 2504 areshown in an alternating, interdigitated pattern, though this is merelyone example configuration for the first and second drive regions 2502,2504.

The sensor 2302 also includes sensing regions 2506. The sensing regions2506 capacitively couple to the drive regions 2502, 2504 and may beconnected to circuitry that detects and analyzes signals induced in thesensing regions 2506 by the drive regions 2502, 2504. Each sensingregion 2506 may overlap one first drive region 2502 and one second driveregion 2504. As the drive regions may be driven at different timesand/or with different signals (e.g., signals having differentfrequencies), a single sensing region can provide two distinctcapacitive measurements, each corresponding to a different locationalong the sensor 2302. In this way, the sensor 2302 is pixelated,allowing for more precise force measurements and for detection of alocation of an applied force on the cover 303.

FIG. 26 is a cross-sectional view of an embodiment of the device 100,viewed along line A-A in FIG. 1, showing a display stack 2600 positionedbelow the cover 110. Force and/or touch sensing systems, or componentsthereof, may be incorporated with the display stack 2600 to facilitatetouch and force input detection on the device 100. As described herein,device 100 may include conductive sheets (such as the first drive layer505, FIG. 5) that may facilitate sensing force and/or touch inputs onthe device 100.

The display stack 2600 may include a touch sensor 2602 positionedbetween the cover 110 and a display layer 2604. The touch sensor 2602can include sensors that are each configured to detect user inputs(e.g., touch and/or force inputs), and the locations of the user inputs,on the cover 110. Any suitable touch sensor 2602 can be used. Forexample, in one embodiment, the touch sensor 2602 is formed with adielectric substrate positioned between two electrode layers. Theelectrode layers may be made of any suitable optically transparentmaterial. For example, in one embodiment the electrode layers are madeof indium tin oxide (ITO). Other suitable materials include, but are notlimited to, nanowires or nanowire meshes, a transparent conducting film(e.g., a polymer film), carbon nanotubes, and ultra-thin metal films.

Each electrode layer in the touch sensor 2602 can include one or moreelectrodes. The electrode(s) in one layer are aligned in at least onedirection (e.g., vertically) with respective electrodes in the otherelectrode layer to form one or more capacitive sensors. User inputs, andthe locations of the user inputs, are detected through changes in thecapacitance of one or more capacitive sensors. As will be described inmore detail later, touch and sense circuitry 2632 is coupled to theelectrode layers and configured to receive an output signal from eachcapacitive sensor that represents the capacitance of each capacitivesensor.

One or both of the electrode layers in the touch sensor 2602 may bepatterned. For example, in one embodiment one electrode layer ispatterned into strips positioned along a first axis (e.g., rows) and theother electrode layer is patterned into strips positioned along a secondaxis that is transverse to the first axis (e.g., columns). Capacitivesensors are formed at the intersections of the strips in the twoelectrode layers. User inputs, and the locations of the user inputs, canbe determined based on the capacitance (or changes in capacitance) ofone or more capacitive sensors.

The display layer 2604 can include a front polarizer 2606, a displayelement 2608 attached to a back surface of the front polarizer 2606, anda back polarizer 2610 attached to a back surface of the display element2608. Any suitable display element 2608 can be used. Example displayelements 2608 include, but are not limited to, a LCD element, a LEDelement, an OLED element, or an OEL element. In the illustratedembodiment, the display element 2608 is a LCD element.

In some situations, noise signals that are produced by the displayelement 2608 can electrically couple with the touch sensor 2602. Thiscoupling can adversely impact the detection of user inputs by the touchsensor 2602. To reduce or eliminate the display noise from coupling withthe touch sensor 2602, a conductive layer 2612 can be positioned betweenthe touch sensor 2602 and the front polarizer 2606. The conductive layer2612 may be made of any suitable optically transparent material. Forexample, in one embodiment the conductive layer 2612 is made of ITO.

A sheet of conductive material 2614 is formed or coated over the backsurface of the back polarizer 2610. The sheet of conductive material2614 can be made of any suitable conductive material. For example, inone embodiment, the sheet of conductive material 2614 is made of asilver nanowire film.

The back polarizer 2610 may be made of an electrically insulatingmaterial. The sheet of conductive material 2614 enables the back surfaceof the back polarizer 2610 to function as a conducting surface. As willbe described in more detail below, the conducting surface of the backpolarizer 2610 is used to transmit drive signals for a force sensor thatincludes the conducting surface.

Attached to the back surface of the back polarizer 2610 is a conductiveborder 2616 (which may be the same or similar in structure, materials,function, etc., to the connection element 706, FIGS. 7, 10A). Theconductive border 2616 is positioned along at least a portion of aperimeter or edge of the back polarizer 2610. As will be described inmore detail in conjunction with FIGS. 27-29, the conductive border 2616can be a continuous border that extends around the entire perimeter, orthe conductive border 2616 can include one or more discrete conductivestrips with each conductive strip positioned along a respective portionof the perimeter of the back polarizer 2610.

In the illustrated embodiment, the display stack 2600 extends across theuser-viewable region 108 (FIG. 1) of the display 102 and intonon-viewable regions 2618 that do not correspond to a viewable outputfrom the display 102. Alternatively, in some embodiments, only a subsetof the layers in the display stack 2600 extend into the non-viewableregions 2618. For example, portions of the display layer 2604 can extendinto the non-viewable regions 2618 while other layers in the displaystack 2600 do not extend into the non-viewable regions 2618.

In some embodiments, the conductive border 2616 can be positioned on theportions of the back polarizer 2610 that reside in the non-viewableregions 2618, which allows the conductive border 2616 to be formed withany suitable material or materials (e.g., opaque or transparentmaterial(s)). For example, the conductive border 2616 may be formed witha metal or metal alloy, such as copper, aluminum, molybdenum, and nickelvanadium. Other embodiments can form at least a portion of theconductive border 2616 within the user-viewable region 108. In suchembodiments, at least the portion of the conductive border 2616 that isin the user-viewable region 108 may be formed with an opticallytransparent material, such as ITO.

In the illustrated embodiment, a backlight unit 2620 is positioned belowthe back polarizer 2610 and the conductive border 2616. The displaylayer 2604, along with the backlight unit 2620, is used to output imageson the display 102. In some implementations, the backlight unit 2620 maybe omitted.

A first electrode layer 2622 is positioned below and attached to thebacklight unit 2620. In some implementations, the first electrode layer2622 represents an array of electrodes (e.g., two or more electrodes).In other implementations, the first electrode layer 2622 is a singleelectrode. The first electrode layer 2622 can be formed with anysuitable conductive material (opaque or transparent), such as a metal ormetal alloy. Example metals and metal alloys include, but are notlimited to, copper, aluminum, titanium, tantalum, nickel, chromium,zirconium, molybdenum niobium, and nickel vanadium.

Together, the sheet of conductive material 2614 on the back surface ofthe back polarizer 2610 and the first electrode layer 2622 form a forcesensor. The force sensor can be used to detect a magnitude or an amountof force that is applied to the cover 110. When the first electrodelayer 2622 is implemented as an array of electrodes, the sheet ofconductive material 2614 and the first electrode layer 2622 form anarray of capacitive sensors. Each capacitive sensor includes anelectrode formed by the sheet of conductive material 2614 and arespective electrode in the first electrode layer 2622. When a userinput is applied to the cover 110, the cover 110 deflects and a distancebetween the electrodes in at least one capacitive sensor changes, whichvaries the capacitance of that capacitive sensor. For example, in theillustrated embodiment, the gap 2623 varies based on a user inputapplied to the cover 110, which in turn varies the capacitance of atleast one capacitive sensor.

In some embodiments, the first electrode layer 2622 can be used todetect one or more touches on the cover 110. In such embodiments, thetouch-sensing layer 2602 may be omitted since the first electrode layer2622 has a dual function in that it is used to detect both touch andforce inputs.

The device 100 can also include a support structure 2624 (which may bethe same or similar in structure, materials, function, etc., to theframe members 309, 1207, discussed above). In the illustratedembodiment, the support structure 2624 is made from a conductivematerial (e.g., a metal), although other embodiments can form thesupport structure 2624 with a different material, such as a plastic,ceramic, or a composite. In the illustrated embodiment, the supportstructure 2624 extends along a length and a width of the display stack2600, although this is not required. The support structure 2624 can haveany shape and/or dimensions in other embodiments. For example, thesupport structure 2624 may have an opening in which a stiffening membermay be positioned (as described with respect to the frame member 309 andthe stiffening member 312, FIG. 3A).

In the illustrated embodiment, the support structure 2624 has a U-shapedcross-section and is attached to the cover 110 such that the supportstructure 2624 is suspended from the cover 110. In other embodiments,the support structure 2624 may be connected to a component other thanthe cover 110. For example, the support structure 2624 can be attachedto a housing of the device 100 (e.g., the housing 104 in FIG. 1) or to aframe or other support component in the housing.

In some embodiments, the support structure 2624 may be constructed andattached to the cover 110 to define a gap 2626 between the supportstructure 2624 and the first electrode layer 2622. The gap 2626 allowsthe display stack 2600 to flex or move in response to an applied forceon the cover 110. In some embodiments, the first electrode layer 2622may be attached to the support structure 2624 instead of the backlightunit 2620.

The device 100 may also include a battery 2628. The battery 2628provides power to the various components of the device 100. As shown inFIG. 26, a second electrode layer 2630 can be disposed on a top surfaceof the battery 2628. In some embodiments, the amount of force applied tothe cover 110 may be sufficient to cause the display stack 2600 todeflect such that the back polarizer 2610 contacts the first electrodelayer 2622. When the display stack 2600 is deflected to a point wherethe back polarizer 2610 contacts the backlight unit 2620 (or firstelectrode layer 2622 if no backlight unit 2620 is present), the amountof force detected by the force sensor reaches a maximum level (e.g., afirst amount of force). The force sensor cannot detect force amountsthat exceed the maximum level. The deflection of the display stack 2600to a point where the back polarizer 2610 contacts the backlight unit2620 or the first electrode layer 2622 may correspond with the firstprofile 406 of the force versus deflection curve in FIG. 4. For example,the maximum level of force detected by the force sensor that includesthe first electrode layer 2622 and the conductive material 2614 maycorrespond to the point 402 in FIG. 4.

In such embodiments, the second electrode layer 2630 (in conjunctionwith the first electrode layer 2622 or other components) can form asecond force sensor that detects the force that exceeds the first amountof force by associating an amount of deflection between the firstelectrode layer 2622 and the second electrode layer 2630 (e.g., a secondamount of force). For example, in some embodiments, the second electrodelayer 2630 can be used to measure a change in capacitance between thefirst and the second electrode layers 2622, 2630. Alternatively, thesecond electrode layer 2630 may be used to detect a change incapacitance between the back surface 2627 of the support structure 2624and the second electrode layer 2630. The deflection between the firstelectrode layer 2622 and the second electrode layer 2630 (or between theback surface 2627 of the support structure and the second electron layer2630) may correspond to the second profile 408 in FIG. 4.

As described earlier, drive and sense circuitry 2632 is coupled to thetouch sensor 2602. The drive and sense circuitry 2632 may be positionedat any suitable location in the device 100. The drive and sensecircuitry 2632 is configured to provide drive signals to the touchsensor 2602 and to receive output signals from the touch sensor 2602.For example, when the touch sensor 2602 includes an array of capacitivesensors, the drive and sense circuitry 2632 is coupled to eachcapacitive sensor and configured to sense or measure the capacitance ofeach capacitive sensor. A processing device may be coupled to the driveand sense circuitry 2632 and configured to receive signals representingthe measured capacitance of each capacitive sensor. The processingdevice can be configured to correlate the measured capacitances into anamount of force.

Similarly, drive circuitry 2634 is coupled to the sheet of conductivematerial 2614 and is configured to provide drive signals to the backsurface of the back polarizer 2610 (e.g., to the sheet of conductivematerial 2614). In some embodiments, the drive circuitry 2634 is coupledto the conductive border 2616.

Sense circuitry 2636 is coupled to the first electrode layer 2622 and isconfigured to receive one or more output signals from the firstelectrode layer 2622. For example, when the first force sensor includesan array of capacitive sensors, the drive and sense circuitry 2634, 2636are coupled to each capacitive sensor and configured to sense or measurethe capacitance of each capacitive sensor. A processing device may becoupled to the drive and sense circuitry 2634, 2636 and configured toreceive the output signals representing the measured capacitance of eachcapacitive sensor. The processing device can be configured to correlatethe measured capacitances into an amount of force. Like the drive andsense circuitry 2632, the drive circuitry 2634 and the sense circuitry2636 may be situated at any suitable location in the device 100.

The drive signals transmitted on the back surface of the back polarizer2610 (e.g., on the sheet of conductive material 2614) can be decoupledfrom the noise produced by the display element 2608 (e.g., a TFT layer)because the insulating back polarizer 2610 physically separates thesheet of conductive material 2614 from the display element 2608.Additionally, the conductive border 2616 may reduce the contactresistance between the back polarizer 2610 and the sheet of conductivematerial 2614, as well as reduce the sheet resistance of the sheet ofconductive material 2614. Reducing the contact resistance and/or thesheet resistance can increase the suppression of the display noiseproduced by the display element 2608.

With respect to the second electrode layer 2630, drive circuitry 2638 iscoupled to the second electrode layer 2630 and is configured to providedrive signals to the second electrode layer 2630. The drive circuitry2638 can be located at any suitable location in the electronic device100. In some embodiments, the sense circuitry 2636 may be configured toreceive one or more output signals from the first electrode layer 2622.A processing device coupled to the sense circuitry 2636 can beconfigured to receive the output signals and correlate the measuredcapacitances into an amount of force.

FIGS. 27-29 depict example arrangements of the conductive border on thepolarizer 2610 shown in FIG. 26. As shown in FIG. 27, the conductiveborder can include four discrete conductive strips 2702, 2704, 2706,2708 that are formed on a sheet of conductive material 2710 coated overa polarizer 2700. Each conductive strip 2702, 2704, 2706, 2708 is formedalong a respective edge of the polarizer 2700. Although FIG. 27 depictsfour conductive strips, other embodiments are not limited to thisarrangement. Other embodiments can include one or more conductivestrips. The embodiments shown in FIGS. 27-29 may represent embodimentsof the conductive material 2614 and the conductive border 2616 on thepolarizer 2610 in FIG. 26.

In some embodiments, the sheet of conductive material 2710 may be formedwith an anisotropic material that is more conductive in one directioncompared to another direction. In such embodiments, the discreteconductive strip or strips 2702, 2704, 2706, 2708 can be more effectiveat reducing the sheet and/or contact resistance of the sheet ofconductive material 2710.

FIG. 28 depicts a discrete L-shaped conductive strip 2802 that ispositioned on a sheet of conductive material 2804 on a polarizer 2800.In the illustrated embodiment, the conductive strip 2802 is formed alongtwo edges of the polarizer 2800. Other embodiments can include two “L”shaped conductive strips that are arranged to position a conductivestrip along each edge of the polarizer 2800.

FIG. 29 illustrates a continuous conductive border 2902 that ispositioned along the entire edge of the polarizer 2900. In somesituations, the continuous conductive border 2902 may reduce the sheetconductivity and/or the contact resistivity of the sheet of conductivematerial 2904 more effectively than a conductive strip or strips. Theconductive strips 2702, 2704, 2706, 2708 and/or the conductive borders2802, 2902 may form the connection element 706 described above withrespect to FIGS. 7 and 10A.

Although the embodiments shown in FIGS. 26-29 are described inconjunction with a display stack in an electronic device, otherembodiments are not limited to displays. A force sensor can be formedbelow any suitable cover, such as the housing of an electronic device(e.g., the housing 104 in FIG. 1, the trackpad 206 in FIG. 2). Aninsulating substrate may be positioned below the cover. A sheet ofconductive material is formed over a back surface of the insulatingsubstrate to produce a conducting surface on the back surface of theinsulating substrate. In other words, the sheet of conductive materialtransforms the back surface of the insulating substrate into aconducting surface. A conductive border is formed along at least oneedge of the sheet of conductive material and an electrode layer ispositioned below the insulating substrate. The conducting surface of theinsulating substrate and the electrode layer together form a forcesensor that is configured to detect a force input on the cover.

Throughout the foregoing discussion, force sensing devices and contactsensors are described with respect to various examples. However, theseexamples are not meant to be limiting of the particular elements,layers, or components described. For example, components (e.g., layersof the force sensing devices) that are described herein as beingseparate and/or distinct may be combined, and components describedherein as being combined or integrated may be separated. Moreover, somecomponents may be substituted, added, or removed without departing fromthe spirit of the disclosure. For example, as noted above, a displaystructure may be omitted from a force sensing device if the forcesensing device is not integrated with or part of a display device.Furthermore, any individual layer or structure described herein mayinclude one or more sub-layers. For example, a cover may includemultiple sub-layers, including glasses, coatings, adhesives, filters,and the like. As another example, any of the layers or components of theforce sensing devices and contact sensors described herein may besecured to adjacent layers or structures with adhesives, bonding layers,or the like, though such adhesives and bonding layers are notnecessarily described herein.

FIG. 30 depicts example components of an electronic device in accordancewith the embodiments described herein. The schematic representationdepicted in FIG. 30 may correspond to components of the devices depictedin FIGS. 1-2, and indeed any device in which the force sensing describedherein may be incorporated.

As shown in FIG. 30, a device 3000 includes a processing unit 3002operatively connected to computer memory 3004 and/or computer-readablemedia 3006. The processing unit 3002 may be operatively connected to thememory 3004 and computer-readable media 3006 components via anelectronic bus or bridge. The processing unit 3002 may include one ormore computer processors or microcontrollers that are configured toperform operations in response to computer-readable instructions. Theprocessing unit 3002 may include the central processing unit (CPU) ofthe device. Additionally or alternatively, the processing unit 3002 mayinclude other processors within the device including applicationspecific integrated chips (ASIC) and other microcontroller devices.

The memory 3004 may include a variety of types of non-transitorycomputer-readable storage media, including, for example, read accessmemory (RAM), read-only memory (ROM), erasable programmable memory(e.g., EPROM and EEPROM), or flash memory. The memory 3004 is configuredto store computer-readable instructions, sensor values, and otherpersistent software elements. Computer-readable media 3006 also includesa variety of types of non-transitory computer-readable storage mediaincluding, for example, a hard-drive storage device, a solid statestorage device, a portable magnetic storage device, or other similardevice. The computer-readable media 3006 may also be configured to storecomputer-readable instructions, sensor values, force-deflectioncorrelations, and other persistent software elements.

In this example, the processing unit 3002 is operable to readcomputer-readable instructions stored on the memory 3004 and/orcomputer-readable media 3006. The computer-readable instructions mayadapt the processing unit 3002 to perform the operations or functionsdescribed above with respect to FIGS. 1-25 or below with respect to theexample process FIG. 31. In particular, the processing unit 3002, thememory 3004, and/or the computer-readable media 3006 may be configuredto cooperate with the force sensor 3022, described below, to determinean amount of force applied to a user input surface by applying differentforce-deflection correlations based on whether a deflection of the userinput surface is collapsing an air gap in a force sensor or compressinga deformable element. The computer-readable instructions may be providedas a computer-program product, software application, or the like.

As shown in FIG. 30, the device 3000 also includes a display 3008. Thedisplay 3008 may include a liquid-crystal display (LCD), organic lightemitting diode (OLED) display, LED display, or the like. If the display3008 is an LCD, the display 3008 may also include a backlight componentthat can be controlled to provide variable levels of display brightness.If the display 3008 is an OLED or LED type display, the brightness ofthe display 3008 may be controlled by modifying the electrical signalsthat are provided to display elements. The display 3008 may correspondto the upper and/or lower stacks described above.

The device 3000 may also include a battery 3009 that is configured toprovide electrical power to the components of the device 3000. Thebattery 3009 may include one or more power storage cells that are linkedtogether to provide an internal supply of electrical power. The battery3009 may be operatively coupled to power management circuitry that isconfigured to provide appropriate voltage and power levels forindividual components or groups of components within the device 3000.The battery 3009, via power management circuitry, may be configured toreceive power from an external source, such as an AC power outlet. Thebattery 3009 may store received power so that the device 3000 mayoperate without connection to an external power source for an extendedperiod of time, which may range from several hours to several days.

In some embodiments, the device 3000 includes one or more input devices3010. The input device 3010 is a device that is configured to receiveuser input. The input device 3010 may include, for example, a pushbutton, a touch-activated button, a keyboard, a key pad, or the like. Insome embodiments, the input device 3010 may provide a dedicated orprimary function, including, for example, a power button, volumebuttons, home buttons, scroll wheels, and camera buttons. Generally, atouch sensor (e.g., a touchscreen) or a force sensor may also beclassified as an input device. However, for purposes of thisillustrative example, the touch sensor 3020 and the force sensor 3022are depicted as distinct components within the device 3000.

The device 3000 may also include a touch sensor 3020 (e.g., the touchsensor 2602, FIG. 26) that is configured to determine a location of atouch over a touch-sensitive surface of the device 3000. The touchsensor 3020 may include a capacitive array of electrodes or nodes thatoperate in accordance with a mutual-capacitance or self-capacitancescheme. As described herein, the touch sensor 3020 may be integratedwith one or more layers of a display stack or a force sensing device toprovide the touch-sensing functionality of a touchscreen. The capacitivearrays of the touch sensor 3020 may be integrated with the force sensingdevices described above, and may be in addition to the capacitivesensing elements that provide force sensing functionality.

The device 3000 may also include a force sensor 3022 that is configuredto receive and/or detect force inputs applied to a user input surface ofthe device 3000. The force sensor 3022 may correspond to any of theforce sensing devices or force sensors described herein, and may includeor be coupled to capacitive sensing elements that facilitate thedetection of changes in relative positions of the components of theforce sensor (e.g., deflections caused by a force input).

As described herein, the force sensor 3022 may include contact sensorsthat are configured to signal when an air gap has been fully collapsedby a force input. The force sensor 3022, including the contact sensors,may be operatively coupled to the processing unit 3002, which canprocess signals from the force sensor 3022 to determine an amount ofapplied force on the user input surface, as described above.

The device 3000 may also include one or more sensors 3024 that may beused to detect an environmental condition, orientation, position, orsome other aspect of the device 3000. Example sensors 3024 that may beincluded in the device 3000 include, without limitation, one or moreaccelerometers, gyrometers, inclinometers, goniometers, ormagnetometers. The sensors 3024 may also include one or more proximitysensors, such as a magnetic hall-effect sensor, inductive sensor,capacitive sensor, continuity sensor, and the like.

The sensors 3024 may also be broadly defined to include wirelesspositioning devices including, without limitation, global positioningsystem (GPS) circuitry, Wi-Fi circuitry, cellular communicationcircuitry, and the like. The device 3000 may also include one or moreoptical sensors including, without limitation, photodetectors,photosensors, image sensors, infrared sensors, and the like. While thecamera 3026 is depicted as a separate element in FIG. 30, a broaddefinition of sensors 3024 may also include the camera 3026 with orwithout an accompanying light source or flash. The sensors 3024 may alsoinclude one or more acoustic elements, such as a microphone used aloneor in combination with a speaker element. The sensors may also include atemperature sensor, barometer, pressure sensor, altimeter, moisturesensor, or other similar environmental sensor.

The device 3000 may also include a camera 3026 that is configured tocapture a digital image or other optical data. The camera 3026 mayinclude a charge-coupled device, complementary metal oxide semiconductor(CMOS) device, or other device configured to convert light intoelectrical signals. The camera 3026 may also include one or more lightsources, such as a strobe, flash, or other light-emitting device. Asdiscussed above, the camera 3026 may be generally categorized as asensor for detecting optical conditions and/or objects in the proximityof the device 3000. However, the camera 3026 may also be used to createphotorealistic images that may be stored in an electronic format, suchas JPG, GIF, TIFF, PNG, raw image file, or other similar file types.

The device 3000 may also include a communication port 3028 that isconfigured to transmit and/or receive signals or electricalcommunication from an external or separate device. The communicationport 3028 may be configured to couple to an external device via a cable,adaptor, or other type of electrical connector. In some embodiments, thecommunication port 3028 may be used to couple the device 3000 to anaccessory, such as a smart case, smart cover, smart stand, keyboard, orother device configured to send and/or receive electrical signals.

The device 3000 may determine an amount of force applied to a user inputsurface using any appropriate techniques or algorithms. For example, thedevice 3000 may use data, readings, or other information from forcesensing devices, and then apply mathematical formulas or consult modelsor lookup tables to determine an amount of applied force based on theinformation from the force sensing devices. More particularly, oneexample technique for determining an amount of force applied to astructure that includes a force sensing device includes consulting alookup table or other data structure that correlates a sensor value(e.g., a detected capacitance value) to a particular known force. Thelookup table may be populated by a calibration process whereby a knownforce is applied to various locations on the user input surface. Foreach location, the resulting sensor values, which may be referred to ascalibration values, for each pixel or sensing region of the sensor arestored in the lookup table (or other data structure). Accordingly, foreach user input location there exists in the lookup table a set ofcalibration values representing the sensor values of all pixels orsensing regions of the sensor when the sensor is subjected to a knownforce. In some cases, multiple sets of calibration values exist for eachlocation, such as values associated with forces of different knownmagnitudes.

In order to determine an amount of force applied to the user inputsurface during normal operation, a location of a touch event on theinput surface is determined (e.g., with the touch sensor 3020), andcalibration values for that location are used in conjunction with thedetected sensor values to determine the actual applied force. As oneexample, if the detected sensor values corresponding to a touch event ata given location are approximately three times the calibration valuesassociated with a touch event at that location, the device 3000 maydetermine that the applied force is approximately three times largerthan the calibration force.

Another technique for determining an amount of applied force includesdetermining an amount of force applied to each pixel or sensing regionof a sensor, and then adding the force from each pixel or sensing regionto determine the total amount of force applied to that sensor. Wherethis technique is used, the change in distance between two sensingelements may be used in conjunction with a known stiffness of a materialbetween the two sensing elements to determine the force applied to thatpixel or region. As one specific example, a deformable element (e.g.,the deformable element 514, FIG. 5) may be positioned between capacitivesensing elements. The capacitive sensing elements may correspond to thesecond and third sensing elements 512, 515 in FIG. 5, which may becapacitive sense and drive layers, respectively. The capacitive sensingelements may also correspond to the first electrode layer 2622 and theconductive material 2614 in FIG. 26. By measuring a capacitance valuebetween the capacitive sensing elements, the device 3000 can determine adistance (or a change in distance) between the sensing elementsresulting from a force applied to the deformable element. The change indistance can be multiplied by a stiffness of the deformable element(e.g., a constant correlating an expected deflection or deformation ofthe material to a given force) to determine the amount of forcecorresponding to the detected change in distance. As noted above, thesecond and third sensing elements 512, 515 may define a number ofdifferent pixels or sensing regions (e.g., regions 702, FIG. 7).Accordingly, the foregoing technique can be used to determine the forceapplied to each individual pixel or sensing region, and those forces canbe combined (e.g., added) to determine the total amount of force appliedto the user input surface and/or to the sensor.

In some cases, the stiffness (e.g., a stiffness constant) of thedeformable element may be determined for each sensing region. Thus, thedistance measurement for each region may be multiplied by a stiffnessconstant specific to that region, which may improve the accuracy of theforce measurements for each pixel or region, and thus may improve theoverall accuracy of the force sensor. The stiffness constant for eachpixel or sensing region may be determined manually, for example, byapplying a known force to each area of the deformable elementcorresponding to a pixel or sensing region, and measuring the amount ordistance that the deformable element has deflected. In some cases,multiple measurements can be taken at different forces to determine anaverage stiffness constant or a stiffness profile for the deformablematerial. This may increase the accuracy of a sensor as compared tousing the same stiffness constant for each sensing region, as thestiffness may vary from region to region.

Either of the foregoing techniques (e.g., consulting a lookup table orcalculating the force based on a stiffness constant) may be used todetermine the force applied to a given sensor or sensing devicedescribed herein. In embodiments where a device includes multiplesensors, a different technique may be used for each sensor. For example,for the force sensing device 500, which includes first and secondcapacitive sensors 518, 519 (FIG. 5), a lookup table may be used todetermine the force applied to the first capacitive sensor 518, and astiffness-based force calculation may be used to determine the forceapplied to the second capacitive sensor 519. As another example, thedevice of FIGS. 23A-23B includes a sensor 2302 positioned between ahousing and a cover, as well as a sensor within the housing (e.g.,including the first and second sensing elements 2304, 2306 with adeformable element 314 therebetween). In this case, a lookup table maybe used to determine the force applied to the sensor 2303, and astiffness-based calculation may be used to determine the force appliedto the sensor within the housing (e.g., the first and second sensingelements 2304, 2306). Alternatively, a lookup table technique may beused for both sensors.

Where two or more sensors are used, the force values that are determinedfor each sensor may be combined to produce a single value thatrepresents the force applied to the user input surface. For example,with reference to the force sensing device 500 (FIG. 5), the first andsecond capacitive sensors 518, 519 may deflect in response to differentapplied forces. More particularly, the air gaps 506 and 510 (between thefirst and second sensing elements 505, 512) may collapse in response toan applied force having a particular value. Because the air gaps 506,510 are between the first and second sensing elements 505, 512, thefirst capacitive sensor 518 defined by these sensing elements can beused to determine the force up to the particular value. Because thedistance between the first and second sensing elements 505, 512 cannotbe further reduced, however, the first capacitive sensor 518 will notdetect values of applied forces in excess of the particular value. Thesecond capacitive sensor 519, however, may detect force after thecollapse of the air gaps 506, 510. Accordingly, where both the first andsecond capacitive sensors 518, 519 produce force values, the values maybe added together to determine the overall force applied to the forcesensing device 500. The same or a similar process may be used inconjunction with the force sensors described with respect to FIG. 26, inwhich the conductive material 2614 and the first electrode layer 2622form a first force sensor, and the first electrode layer 2622 and thesecond electrode layer 2630 form a second force sensor.

FIG. 31 depicts an example process 3100 for determining an amount offorce applied on a user input surface of an electronic device. Theprocess 3100 may be implemented on any of the example devices discussedherein. The process 3100 may be used, for example, to determine whatactions (if any) the electronic device should perform in response to theforce input, and may be implemented using, for example, the processingunit and other hardware elements described with respect to FIG. 30. Theprocess 3100 may be implemented as processor-executable instructionsthat are stored within the memory of the electronic device.

In operation 3102, it is determined whether a sensor signal correspondsto a deformation of a first spacing layer (e.g., an air gap, asdescribed above) or of a second spacing layer (e.g., a deformableelement, as described above), or a combination of both. For example, thedevice may monitor a rate of change of a sensor signal. If the rate ofchange of the sensor signal satisfies a first condition (e.g., it isconstant over a particular deformation range or it is below a thresholdvalue), the device may determine that an air gap is being or has beencollapsed. If the rate of change of the sensor signal satisfies a secondcondition (e.g., it is increasing over a particular deformation range orit is above the threshold value), the device may determine that an airgap has been fully collapsed and a deformable element has been or isabout to be at least partially compressed. As another example, thedevice may determine whether a sensor signal corresponds to a collapseof a first spacing layer or a second spacing layer based on whether ornot a contact sensor (e.g., the contact sensors described with respectto FIGS. 16 and 18A-22B) indicates that the first spacing layer hasfully collapsed.

In operation 3104, a force-deflection correlation is selected. Asdescribed herein, a different force-deflection correlation may be usedto determine an amount of applied force, depending on whether thedeflection of the force sensor corresponds to a collapse of a firstspacing layer (e.g., an air gap) or deformation of a second spacinglayer (e.g., a deformable element). Thus, if the device determines atoperation 3102 that the sensor signal corresponds to a deformation ofthe first spacing layer, such as the collapse of an air gap, the devicemay at operation 3104 select a first force-deflection correlation. Ifthe device determines at operation 3102 that the sensor signalcorresponds to a deformation of the second spacing layer, such ascompression of a deformable element, the device may at operation 3104select a second force-deflection correlation that is different than thefirst.

In embodiments where the device includes multiple sensors spanningdifferent spacing layers (such as the first and second capacitivesensors 518, 519, FIG. 5), the device may select and use multipleforce-deflection correlations. For example, if the device determines atoperation 3102 that the deflection corresponds to an at least partialcollapse of both a first and a second spacing layer, the device mayselect an appropriate force-deflection correlation for each sensor.

In operation 3106, an amount of applied force is determined based on theselected force-deflection correlation(s). For example, the devicecorrelates the amount of deflection indicated by the sensor signal to aparticular applied force by using a lookup table, a stiffness-basedforce calculation, or another technique that implements the selectedforce-deflection correlation. In embodiments where the device includesmultiple sensors, the device may correlate the amount of deflectionindicated by each sensor with a force value, and then add the forcevalues from each sensor to determine the total amount of applied force.

Based on the determined amount of applied force, the device may perform(or not perform) certain actions. For example, if the applied force islower than a threshold value, the device may perform one action, and ifthe applied force is higher than the threshold value, the device mayperform another action. As one example, if the force is lower than thethreshold value, the device may move a cursor to a positioncorresponding to the location of the touch event, whereas if the forceis higher than the threshold value, the device may register a selection(e.g., a mouse click) at the location of the cursor. This is merely oneexample, however, and the range of possible actions that the device canperform based on the determined amount of applied force are limited onlyby the capabilities of the device.

As noted above, force sensors may use sheets or layers with conductiveborders. For example, as described with respect to FIGS. 7, 10A, and26-29, conductive sheets may be used as drive layers for capacitiveforce sensing systems. Conductive borders may be applied to or otherwiseincluded in the conductive sheets. FIG. 32 shows a flowchart of a methodof manufacturing the conductive borders on a surface of a sheet, such asa polarizer as described with respect to FIGS. 26-29 or a force sensingelement 505 described with respect to FIGS. 5, 7, and 10A. FIG. 32 willbe described in conjunction with FIGS. 33-37. The method is described inconjunction with a roll-to-roll production process. Although describedin conjunction with a polarizer, the process can be used to produce aconductive border on any suitable film or substrate. Additionally, themethod is described in conjunction with forming continuous conductiveborders (e.g., see FIGS. 7, 29), although embodiments are not limited tothis type of conductive border.

In other embodiments, a conductive border can be fabricated on apolarizer or substrate using other manufacturing processes. Examplemanufacturing processes include, but are not limited to, physical orchemical vapor deposition, screen printing or inkjet coating technologyusing a shadow mask, and film mask and photolithography.

Initially, as shown in block 3200, masks are applied to a surface of afilm. In one embodiment, the film is a polarizer film that includes asheet of conductive material formed or coated over a surface of thepolarizer film. As describe earlier, the polarizer film will be attached(e.g., laminated) to the back surface of a display element and functionas a polarizer for the display (e.g., display element 2608 and backpolarizer 2610 in FIG. 26).

Each mask defines the area that will be surrounded by, or inside of, theconductive border. For example, the masks can define the user-viewableregion (e.g., the user-viewable region 108) of a display. Althoughdepicted as having a rectangular shape, a mask can have any given shapeand/or dimensions.

In some embodiments, each mask can be one of multiple masks. Forexample, when forming multiple conductive strips (e.g., see FIG. 27) ona film substrate, a mask defines the area that will not include theconductive strips.

FIGS. 33A-33B depict the application of masks to a surface of a film. Asshown in FIG. 33A, the application process 3300 includes moving the film3302 from a first roller 3304 towards a second roller 3306 in aroll-to-roll production system. This movement is represented in FIGS.33A and 33B by arrow 3308. In one embodiment, the second roller 3306includes the finished product of the method shown in FIG. 32 (e.g., acollection of conductive borders formed on the surface of the polarizerfilm). In another embodiment, the second roller 3306 includes acollection of masks formed on the surface of the film (e.g., thefinished product of block 3200).

A third roller 3310 is positioned between the first and the secondrollers 3304, 3306. The third roller 3310 includes a collection of masks3312 that are applied to the film 3302 as the film 3302 moves below thethird roller 3310. FIG. 33B illustrates a top view of the film 3302after the masks 3312 have been applied to the film 3302 by the thirdroller 3310.

Referring now to block 3202 in FIG. 32, a conductive material is formedover the masks and the surface of the film. The conductive material isthe material used to form the conductive borders. FIGS. 34A-34B show theformation of the conductive material over the film and the masks. Theformation process 3400 includes moving the film 3302 from a fourthroller 3402 towards a fifth roller 3404 (movement represented by arrow3406). In one embodiment, the fourth roller 3402 corresponds to thefirst roller 3304 and the fifth roller 3404 corresponds to the secondroller 3306. In such embodiments, the fifth roller 3404 includes acollection of conductive borders formed on the surface of the polarizerfilm (e.g., the finished product of the method shown in FIG. 32). Inother embodiments, the fourth roller 3402 includes the finished productof block 3200.

In the illustrated embodiment, the film 3302 with the masks 3312 entersa deposition chamber 3408 where a nozzle 3410 deposits the conductivematerial 3412 onto the film 3302 and the masks 3312. The deposition canbe a blanket deposition such that the entire film 3302 and masks 3312have conductive material deposited thereon. FIG. 34B illustrates a topview of the film 3302 after the conductive material 3412 has beendeposited onto the film 3302 and the masks 3312 by the depositionchamber 3408.

Referring now to block 3204 in FIG. 32, the masks are removed from thesurface of the film after the conductive material has been formed overthe masks and the film. FIGS. 35A-35B show the removal of the masks 3312from the film 3302. The removal process 3500 includes moving the film3302 from a sixth roller 3502 towards a seventh roller 3504 (movementrepresented by arrow 3506). In one embodiment, the sixth roller 3502corresponds to the first roller 3304 and the seventh roller 3504corresponds to the second roller 3306. In such embodiments, the seventhroller 3504 includes the finished product of the method shown in FIG.32. In other embodiments, the sixth roller 3502 includes the finishedproduct of block 3202.

An eighth roller 3508 is positioned between the sixth and seventhrollers 3502, 3504. The eighth roller 3508 removes the masks 3312, whichleaves regions 3514 that include only the film 3302. The conductivematerial is disposed on the areas around the regions 3514. FIG. 35Billustrates a top view of the film 3302 after the masks 3312 have beenremoved by the eighth roller 3508.

Any suitable process can be used to remove the masks 3312. For example,in one embodiment, the eighth roller 3508 employs an electrostatictechnique to remove the masks 3312.

In some embodiments, an imaging system (e.g., a camera) can bepositioned over the film 3302 between the eighth roller 3508 and theseventh roller 3504. The imaging or automated optical inspection systemmay be used to inspect the film for defects after the masks have beenremoved by the eighth roller 3508.

Referring now to block 3206 in FIG. 32, a protective layer is formedover the surface of the film and the conductive material. FIGS. 36A-36Bshow the formation of the protective layer over the film and theconductive material. The formation process 3600 includes moving the film3302 from a ninth roller 3602 towards a tenth roller 3604 (movementrepresented by arrow 3606). In one embodiment, the ninth roller 3602corresponds to the first roller 3304 and the tenth roller 3604corresponds to the second roller 3304. In such embodiments, the tenthroller 3604 includes the finished product of the method shown in FIG.32. In other embodiments, the ninth roller 3602 includes the finishedproduct of block 3204.

An eleventh roller 3608 is positioned between the ninth and tenthrollers 3602, 3604. The eleventh roller 3608 applies the protectivelayer 3610 over the film 3302 and the conductive material 3412. FIG. 36Billustrates a top view of the film 3302 after the protective layer 3610has been applied by the eleventh roller 3608.

Referring now to block 3208 in FIG. 32, the conductive borders are cut(e.g., singulated) to produce individual sections of film that are eachsurrounded by a conductive border. FIGS. 37A-37B show the production ofeach individual section of film that is surrounded by a conductiveborder. The cutting process 3700 includes moving the film 3302 from atwelfth roller 3702 towards a thirteenth roller 3704 (movementrepresented by arrow 3706). In one embodiment, the twelfth roller 3702corresponds to the first roller 3304 and the thirteenth roller 3704corresponds to the second roller 3306. In such embodiments, thethirteenth roller 3704 includes the finished product of the method shownin FIG. 32. In other embodiments, the twelfth roller 3702 includes thefinished product of block 3206.

In the illustrated embodiment, a singulation system 3708 is positionedover the film 3302 between the twelfth roller 3702 and the thirteenthroller 3704. The singulation system 3708 includes a precision die cuttool 3710 that is aligned by one or more alignment cameras 3712.

In one embodiment, the precision die cut tool 3710 uses one or morecorners of the regions 3514 (FIG. 35) as a cut reference 3714 toposition the die cut pattern 3716. FIG. 37B illustrates top view of thefilm 3302 with the cut references 3714 and die cut pattern 3716 beforethe die cut tool 3710 cuts the individual sections. Two singulatedsections 3718 are also depicted in FIG. 37B. Each singulated section3718 includes a section of film 3720 surrounded by a conductive border3722. As described earlier, the section of film 3720 includes a sheet ofconductive material formed over a polarizer film (e.g., the sheet ofconductive material 2614 coated over the back polarizer 2610 in FIG.26).

Referring to block 3210 in FIG. 32, each singulated section may then beattached to a display layer. In particular, each singulated section canbe laminated to a back surface of a back polarizer in the display layer.

The geometry of the mask (e.g., mask 3312 in FIG. 33B) and/or thegeometry of the die cut pattern (e.g., die cut pattern 3716 in FIG. 37B)can be varied to adjust the geometry of the conductive border. FIGS.38-40 show example techniques for determining the geometry of theconductive border. In FIG. 38, the die cut pattern 3800 is a rectangularshape that is situated to center the mask 3802 in the center of the diecut pattern 3800. After the singulation process is performed, the film3806 includes a continuous rectangular conductive border 3804 thatextends along the edges of the film 3806.

As shown in FIG. 39, the die cut pattern 3900 is offset from the mask3902 such that one edge of the mask 3902 is outside the die cut pattern3900. After the singulation process is performed, the film 3906 includesa U-shaped conductive border 3904. In the illustrated embodiment, thetop edge of the mask 3902 is located outside the die cut pattern 3900 toproduce a U-shaped conductive border 3904 that extends along the twoside edges and the bottom edge of the film 3906. However, otherembodiments are not limited to this presentation. The shape andorientation of the conductive border 3804 determines which edge (oredges) of the mask 3902 are located outside of the die cut pattern 3900.

FIG. 40 illustrates a die cut pattern 4000 that situates three of thefour edges of the mask 4002 outside of the die cut pattern 4000. Afterthe singulation process is performed, the film 4006 includes a linearconductive border 4004 that extends along one edge of the film 4006. Inthe illustrated embodiment, only a portion of the bottom edge of themask 4002 is positioned within the die cut pattern 4000 to produce alinear conductive border 4004 that extends along the bottom edge of thefilm 4006. However, other embodiments are not limited to thisconfiguration. The shape and orientation of the conductive borderdetermines which edge (or edges) of the mask 4002 are located outside ofthe die cut pattern 4000.

The foregoing description, for purposes of explanation, uses specificnomenclature to provide a thorough understanding of the describedembodiments. However, it will be apparent to one skilled in the art thatthe specific details are not required in order to practice the describedembodiments. Thus, the foregoing descriptions of the specificembodiments described herein are presented for purposes of illustrationand description. They are not targeted to be exhaustive or to limit theembodiments to the precise forms disclosed. It will be apparent to oneof ordinary skill in the art that many modifications and variations arepossible in view of the above teachings. Also, when used herein to referto positions of components, the terms above and below, or theirsynonyms, do not necessarily refer to an absolute position relative toan external reference, but instead refer to the relative position ofcomponents with reference to the figures.

What is claimed is:
 1. An electronic device, comprising: a user inputsurface defining an exterior surface of the electronic device; a firstcapacitive sensor comprising a first pair of sensing elements having anair gap therebetween and configured to determine a first amount ofapplied force on the user input surface that results in a collapse ofthe air gap; and a second capacitive sensor below the first capacitivesensor comprising a second pair of sensing elements having a deformableelement therebetween and configured to determine a second amount ofapplied force on the user input surface that results in a deformation ofthe deformable element.
 2. The electronic device of claim 1, wherein:the first pair of sensing elements comprises: a shared sense element;and a first drive element set apart from and capacitively coupled to theshared sense element; and the second pair of sensing elements comprises:the shared sense element; and a second drive element set apart from andcapacitively coupled to the shared sense element.
 3. The electronicdevice of claim 2, further comprising: a display layer comprising: adisplay element positioned below the user input surface; and a backpolarizer positioned below the display element; a sheet of conductivematerial formed over a back surface of the back polarizer to produce aconducting surface on the back surface of the back polarizer; and aconductive border formed along at least one edge of the sheet ofconductive material.
 4. The electronic device of claim 3, wherein theconductive border is positioned outside of a user-viewable region of thedisplay layer.
 5. The electronic device of claim 3, wherein the sheet ofconductive material comprises silver nanowire.
 6. The electronic deviceof claim 2, further comprising: a display element coupled to the firstdrive element; and a base structure, wherein: the display element isconfigured to flex relative to the base structure; the deformableelement is coupled to the base structure; and the air gap is positionedbetween the deformable element and the display element.
 7. Theelectronic device of claim 6, wherein the shared sense element iscoupled to the deformable element.
 8. A capacitive force sensor for anelectronic device, comprising: a first drive layer; a second drive layerpositioned relative to the first drive layer; a shared sense layerbetween the first and second drive layers; a first spacing layer betweenthe first drive layer and the shared sense layer; and a second spacinglayer between the shared sense layer and the second drive layer.
 9. Thecapacitive force sensor of claim 8, wherein: the first spacing layercomprises an air gap; and the capacitive force sensor further comprises:a pair of opposed surfaces defining the air gap; and an anti-adhesionlayer configured to prevent adhesion between the opposed surfaces. 10.The capacitive force sensor of claim 9, wherein the second spacing layercomprises an array of deformable protrusions extending from a baselayer.
 11. The capacitive force sensor of claim 8, further comprisingsensing circuitry operatively coupled to the first drive layer, thesecond drive layer, and the shared sense layer, and configured todetermine: a first amount of applied force resulting in a change inthickness of the first spacing layer; and a second amount of appliedforce resulting in a change in thickness of the second spacing layer.12. The capacitive force sensor of claim 6, wherein the first drivelayer comprises: an insulating substrate; a sheet of conductive materialformed over a back surface of the insulating substrate to produce aconducting surface on the back surface of the insulating substrate; anda conductive border formed along at least one edge of the sheet ofconductive material.
 13. The capacitive force sensor of claim 12,wherein the conductive border comprises a continuous conductive borderthat extends along the edges of the sheet of conductive material. 14.The capacitive force sensor of claim 12, wherein the conductive bordercomprises one or more conductive strips formed along a respective edgeof the sheet of conductive material.
 15. An electronic device,comprising: a cover defining a user input surface of the electronicdevice; a first sensing element coupled to the cover within an interiorvolume of the electronic device; a frame member coupled to the cover andextending into the interior volume of the electronic device; a secondsensing element coupled to the frame member; and a third sensing elementcoupled to a base structure and set apart from the sense layer.
 16. Theelectronic device of claim 15, wherein: the frame member defines anopening; and the third sensing element capacitively couples with thesecond sensing element through the opening.
 17. The electronic device ofclaim 15, wherein the first sensing element comprises a continuous layerof transparent conductive material covering substantially an entiresurface of a substrate.
 18. The electronic device of claim 17, wherein:the second sensing element comprises a plurality of sensing regions; andthe continuous layer of transparent conductive material overlapsmultiple sensing regions of the plurality of sensing regions.
 19. Theelectronic device of claim 18, wherein: the third sensing elementcomprises a plurality of drive regions; and each drive region overlapsmultiple sensing regions of the plurality of sensing regions.
 20. Theelectronic device of claim 17, wherein: the first sensing elementfurther comprises a connection element electrically coupled to thecontinuous layer of transparent conductive material; and the electronicdevice further comprises: sensing circuitry configured to provide anelectrical signal to the first sensing element; and a connector segmentelectrically coupling the sensing circuitry to the connection element.